front blower mystery-resistor bypass?

[Previologist]

normally when the resistor is shot, the front blower will only work on high. My blower only works on high. However, I bought a new resistor and it still only blows on high.

The previous idiot...I mean previous owner...altered the wiring for reasons I know not. The resistor wiring is untouched, but the wiring to the blower itself was cut and the connector removed, and an entirely new wire installed that runs to the blower. I'm guessing (and only guessing, because I am not in possession of electrical know-how) that the resistor might be completely bypassed, therefore installing a new one did nothing.

I know there is also a blower switch somewhere that sometimes burns out, but I've never heard of that causing all of the lower speeds to go out while leaving high speed intact. That's usually resistor. And getting at the switch isn't fun, so I'm not itching to try.

Given my limited electrical know how, is there a simple way to test whether the resistor has simply been bypassed? If it has i could then contemplate whether I have the smarts to remedy that....I suppose tracing the new wire to the blower might be a first step.

[originalkwyjibo]

I suppose tracing the new wire to the blower might be a first step.

This would be a good start. You may find the original wiring in the process.You could also test for voltage at the resistor itself. Unfortunately, figuring out and fixing other people's "repairs" is typically not a fun job.

[Previologist]

Being 4 terminals at the resistor and me having only half a brain, i would need instructions on how to test the resistor connector for voltage. If there were only 2 that would mean i only have a 50% chance of getting it wrong but with 4...thats the wild west, to me.

I'm pretty sure I saw where the new wire came from while I was doing something else, but I didn't pay close attention at the time. I will check again tomorrow. They also ran it in a different location than the original harness so it should be easy to trace

[originalkwyjibo]

There are three resistors on the resistor pack each of a different resistance value, one for each of the three lower fan speeds. There is one terminal connected to each of the three low speed outputs of your fan switch. The forth terminal is the ouput to the fan. All three resistors are tied to the output terminal on one side. When the fan switch sends voltage to the resistor pack, it flows through the appropriate resistor and a reduced voltage is sent to the fan. Without knowing which terminal is which, just check all four. Ground your voltmeter negative lead to the chassis and with the fan on any position except high, probe all four terminals of the resistor pack with the voltmeter positive lead. Repeat for each fan speed. If there is no voltage at anytime, it is indeed bypassed.

[Previologist]

No power to the resistor connector, as I suspected. I haven't found where those wires originate, and may not be able to.

I traced one of the new blower wires to the front heater relay. The other one runs under the instrument panel and I presume goes to ground. Still trying to trace it

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/previa%20electrical/IMG_0311.jpg

[Previologist]

So here's the setup. One of the new red wires runs from a terminal inside the Front Heater Relay to the blower, and the other new red wire is crimped to a presumably original blue/ wire that is apparently (I can't see) soldered into the underside of the Front Heater (HI) relay next to it.

10594

I couldn't find the origin point of the original wires, although I presume (perhaps incorrectly) that the blue one is part of it. I found no disconnected wires.

Here is the new wiring from the relays to the blower, seen under the hood. They ran them through the firewall with the cable that opens the fresh air flapper.

10595

And here is the original wiring near the resistor, with the resistor connector intact and the blower wires cut.

10596

So now what? I can't help wonder why they did this in the first place, and if that holds the key to what to do next. But that might be giving the previous owner, who also owned the shop that did this, too much credit. and I'm not sure I have the electrical skills to fix this myself

[Jonny]

Did you get this fixed yet?

I wonder if they did all this to "fix" a failed resistor. That seems the most likely explanation.
The resistor is inside the blower housing. Taking the blower out is required to see what's going on.

When looking at the resistor, the 4 terminals are marked H, M2, M1, and L on the plastic plate. Test resistance between H and M2, H and M1, H and L. Resistance is really small, like 1 - 2 ohms or something, and you should see a slight increase in resistance doing them in this order as you move through the terminals.

Pic of a smashed apart resistor to see the workings. This was all encapsulated in porcelain or something before it ran into a hammer. Basically it's a bunch of coils in series. The terminals/fan switch include or exclude coils to increase or decrease resistance in the circuit. That beefy looking "5th terminal" is simply a support for the big coils and just mounts directly into the plastic.
10814


Here are the terminals. The supporting thingy goes to the point marked PM (connects to nothing)
10815

If it was me, I'd take your current blower out and test the resistor to verify whether your problem is indeed there, or not.
If not, I'm out of ideas.
If so, find a complete spare blower assembly from the scrap yard (so you have a spare motor, too), test the motor and resistor to verify function, wait until a point in the year when you can live without heat or AC for a couple of days so that it doesn't matter if things don't go according to plan, and reinstall everything back to stock. Maybe just clip out the existing wiring minimally so you can easily return it to the high speed only situation if for some reason the new parts don't fix the blower speeds problem. (I can't imagine why it wouldn't, but with my modest understanding of electrical stuff that doesn't mean much!). Looks like you might have to solder or crimp to that blower harness wire.

[Previologist]

Did you get this fixed yet?


No its not fixed, I'm currently worrying about other things like where to get the money to replace my engine for this van that I got ripped off on. But I would like to fix it.

However I think I explained above, or I meant to, that I bought a new resistor hooked it up and it didn't work either. I never mounted it, and had been driving without a resistor and high fan speed only until the head gasket blew. But I don't think there was anything wrong with the old resistor.

So I have both of them here in front of me and with my analog meter I don't pick up any resistance on any of the terminals on either of them. I doubt the new one is bad, maybe you are testing a bad one? Also I'm pretty sure there were no fan speeds at all before they did this sloppy "repair", because I have the receipt saying they repaired it by running the new wire. haha. So that suggests it wasn't the resistor

[Jonny]

It looks like I need to learn to read, eh? Especially the first paragraph of the first post!

I looked at the wiring diagram and when the switch is in high position it activates the "heater high relay" providing a separate no-resistance path to ground, effectively bypassing the whole resistor part of the deal. What I'm not so clear on is the "heater relay", but I believe that it is activated whenever the blower switch is at any setting except off, and sends current through the resistor to ground. The high setting and heater high relay just creates the other bypass in addition.

Since the new wiring seems to be related to the two relays I wonder if this is what they did....
i) solder the contacts together on the under side of the "heater relay" so that it is always closed.
ii) cut the original motor wire as the easiest way of disabling the original circuitry.
iii) run new wires from the relays to the motor so that the stratagem for high-only function comes to fruition.
The question remains why? Maybe there was an undiagnosed electrical gremlin unrelated to relays and resistors and this was the expedient way of getting at least some blower function. There must have been something unusual going on or you'd think they would have found the culprit component and just replaced it.

Did you test the relays, just to be sure about them, too (the heater relay especially)?

Re: the resistor terminal resistance values. They're really small. It surprised me how small they are. 1/2 an ohm between H and M2, 2 ohms between H and L. Maybe it's a meter sensitivity thing? Would have been nice if the manual gave an idea of the values one is meant to see, but it doesn't. It just shows you should be seeing some resistance. At least that's the way it is in the '93 manual I'm looking at.

Edit: I realize now that if the red wire in your first pic goes from the battery positive side of the heater relay to the positive side of the fan it would bypass the heater relay and create an always live motor just waiting for the heater high relay to be activated by the high switch setting. Basically since the original wires were cut the entire system may have been reduced to a simple circuit with an on/off switch, the switch high setting / heater high relay acting as that switch. A faulty heater relay would cause failure of all fan speeds and is beginning to look suspicious, but if that's the case someone went to a lot of trouble to avoid spending $25 for a new one. It still doesn't make sense. Sometimes though, I suppose, it doesn't have to.

[Previologist]

Yeah my analog meter might just not pick up a resistance reading that small, so its possible that it was there.

I did not test the relays. I'm electrically challenged and would need instructions.

Let me tell you some of what else they did, and going to a lot of trouble to avoid a $25 (actually closer to 50) relay might not seem so unthinkable.

They installed a rebuilt engine and never hooked up the oil pressure sensor, and either removed or never replaced the check engine light bulb. They installed SADS couplings and within 2 months all but one bolt had broken and it damn near came off. The head gasket on the rebuilt engine blew after less than 8000 miles.

Nothing would surprise me at this point. The seller, who owned the shop that did this work, is either an incompetent shop owner or an unethical bamboozler, or both.

[Previologist]

It looks like I need to learn to read, eh? Especially the first paragraph of the first post!

I looked at the wiring diagram and when the switch is in high position it activates the "heater high relay" providing a separate no-resistance path to ground, effectively bypassing the whole resistor part of the deal. What I'm not so clear on is the "heater relay", but I believe that it is activated whenever the blower switch is at any setting except off, and sends current through the resistor to ground. The high setting and heater high relay just creates the other bypass in addition.

Since the new wiring seems to be related to the two relays I wonder if this is what they did....
i) solder the contacts together on the under side of the "heater relay" so that it is always closed.
ii) cut the original motor wire as the easiest way of disabling the original circuitry.
iii) run new wires from the relays to the motor so that the stratagem for high-only function comes to fruition.
The question remains why? Maybe there was an undiagnosed electrical gremlin unrelated to relays and resistors and this was the expedient way of getting at least some blower function. There must have been something unusual going on or you'd think they would have found the culprit component and just replaced it.

Did you test the relays, just to be sure about them, too (the heater relay especially)?

Re: the resistor terminal resistance values. They're really small. It surprised me how small they are. 1/2 an ohm between H and M2, 2 ohms between H and L. Maybe it's a meter sensitivity thing? Would have been nice if the manual gave an idea of the values one is meant to see, but it doesn't. It just shows you should be seeing some resistance. At least that's the way it is in the '93 manual I'm looking at.

Edit: I realize now that if the red wire in your first pic goes from the battery positive side of the heater relay to the positive side of the fan it would bypass the heater relay and create an always live motor just waiting for the heater high relay to be activated by the high switch setting. Basically since the original wires were cut the entire system may have been reduced to a simple circuit with an on/off switch, the switch high setting / heater high relay acting as that switch. A faulty heater relay would cause failure of all fan speeds and is beginning to look suspicious, but if that's the case someone went to a lot of trouble to avoid spending $25 for a new one. It still doesn't make sense. Sometimes though, I suppose, it doesn't have to.

I wonder if this could simply be a bad speed control switch? The shop that did this work is completely incompetent and its possible they went to all this trouble because they couldn't find a switch. Its not usual for all the low speeds to go out when the switch goes bad and that's why I've been ignoring that possibility but i suppose its possible.

I will pull the relay to see if your guess about soldering it is correct, but that would suggest a mixture of incompetence and problem solving that I don't think they possessed. How do I test the relay?

[Jonny]

We can get this figured out. First, let us know if you have a repair manual.

[Previologist]

I don't have a hard copy, but I think I may have access to the pdf manual in 1000 pieces for the 96 that used to be on the yahoo site. Now if only i could remember where it is...

OK, found it.

[Jonny]

I was going to point you to the page of the manual where the relay testing instructions were, but looking at my '91 manual there is an unfortunate typo and the testing method is subsequently wrong!

Below is a photo of the main heater relay (the left one in the photo of the relay bank as you noted in post #5) sitting atop the page of my manual showing the internal wiring, which is correct!

11109

Most relays work the same way - a low current circuit with a coil induces a magnetic field in the coil when electrified, and the magnetic field causes a separate internal switch to close which completes the high current circuit used to operate the device.

In your relay, the low current circuit is between posts 1 and 3, and the high current circuit is between posts 4 and 5.

With the relay just sitting in front of you not connected to anything, you should see continuity with some resistance between 1 and 3, and continuity with basically no resistance between 2 and 4.
Now carefully connect 1 and 3 to a 12 v battery (polarity when connecting doesn't matter for this test) and you should hear a distinct click as the internal switch operates. While 1 and 3 are still connected to the battery you should also have negligible resistance between 4 and 5. This shows that the internal switch and its contacts are functioning and current is being allowed to flow between 4 and 5.

[Previologist]

Thanks. Everything checks out. And to make sure of what I was doing, I checked the resistance between 4 and 5 when the power was off, and there was infinite resistance, but little to none with the power on. So the relay seems to be working.

[Jonny]

Good. One item to rule out.

If you have page 19 of the wiring diagrams at the back of the manual, take a look at that.
If not, here it is anyway from my manual...

11110

The following comments are based on the original wiring before it was all cut up..

Power comes from the battery (not in photo), through the ignition "on" switch (partly obscured by the paint can holding the book open), through the 40A circuit breaker (on the right side of the pic) to the main relay you have just tested. The relay has power on the battery + side but is waiting for the coil circuit of the relay to be activated in order for the switch to close.

The Y-B wire coming out of the lower right side of the relay coil goes via the 15A A/C fuse (off photo lower right) to the ignition and is live when the ignition is on. If you follow the Y-L wire out of the other side of the coil it goes to the blower switch, so the blower switch + side is actually live all the time too. Note that when you put the blower switch into any of the lower speeds, the coil circuit is completed via the slide contacts (shown by rectangular bars in the diagram) and the W-B wire to ground. With the main relay switch now on, the motor circuit is completed via the motor and the resistor. The current can't take the other fork of the L-B wire because the Heater HI relay is open.

When the blower switch is in the HI position the heater high relay also turns on and the motor current is allowed to bypass the resistor portion of the circuit completely.

So back to your problem...
Since the main relay works, and the heater high relay works, you're looking at resistor or switch as most likely reasons the wiring bypass was done. I suspect you are right that the resistor is fine - I think you would have picked up an open circuit with your meter had there been a problem. That leaves the switch itself as the last likely culprit. Dashboard surgery might be in your future if you want to pursue this further.

[Previologist]

Before going in any further I should ask what would I do if I found out the switch was bad, which seems likely, because they have whacked off the original harness that goes to the switch. I wonder if I might finally get in over my head if I continue...

[Jonny]

Well, if your intent is to return the blower to full functionality and stock circuitry, you'd buy a new switch (8473295D00 $83, or get one from the scrap yard) and determine all the parts of the wiring harness which have been cut so that you can replace those too. Depending on what exactly was cut it seems like you might at least need a scrap yard blower motor harness sub-assembly (see attachment).
https://parts.toyota.com/a/Toyota_1997_Previa-DELUXE/_52016_6709035/HEATING--AIR-CONDITIONING---HEATER-UNIT--BLOWER/652440-8712.html
There is nothing to lose except time and patience by at least taking the dash apart to inspect the switch. It's a bit of a pain, but the van is still drivable with the center dash partially disassembled, so you don't have to worry about getting it done all at once.
https://www.toyotavantech.com/forum/showthread.php?145-How-to-disassemble-the-dash-on-a-Previa&highlight=disassemble+dash

If you would like, and depending on how frequently Previas show up in your area, I can go to the yard next time a Previa shows up in SLC and look for some stuff for you. Send me an email.

[Previologist]

its not the switch itself that scares me, its the prospect of replacing the harness. If I can use the jury-rigged wire to run off a good switch (which I probably have, in my 93) that would be somewhat less intimidating. Being nearly electrically illiterate doesn't boost my confidence.

[Jonny]

Finding the faulty component is still necessary. Check out whether the switch is bad - it's usually the pigtail connector contacts which burn up - and decide from there. This thread also has switch and dash disassembly info...
https://www.toyotavantech.com/forum/showthread.php?3918-blower-speed-and-air-conditioning-switch&highlight=switch+blower

[John Kaufmann]

Finding the faulty component is still necessary. Check out whether the switch is bad - it's usually the pigtail connector contacts which burn up - and decide from there. This thread also has switch and dash disassembly info...
https://www.toyotavantech.com/forum/showthread.php?3918-blower-speed-and-air-conditioning-switch&highlight=switch+blower
Jonny, I checked out the thread you linked, and have to say how impressed I am with your post #7. I went a different way, disconnecting all of the lever cables so that i could pull the HVAC control assembly and work on it. Your approach -- removing the switch without removing the HVAC assembly -- was very nice, and the write-up was terrific.

I will say, though, having gone to all that work (either way), I would just spend the $50 or so (at Autozone) for a new switch, rather than trying to repair the old one or put in a used one.

[Previologist]

Finding the faulty component is still necessary. Check out whether the switch is bad - it's usually the pigtail connector contacts which burn up - and decide from there. This thread also has switch and dash disassembly info...
https://www.toyotavantech.com/forum/showthread.php?3918-blower-speed-and-air-conditioning-switch&highlight=switch+blower

Yeah I'll get around to it eventually. Thanks for the guidance.

[TheMAN]

Jonny, I checked out the thread you linked, and have to say how impressed I am with your post #7. I went a different way, disconnecting all of the lever cables so that i could pull the HVAC control assembly and work on it. Your approach -- removing the switch without removing the HVAC assembly -- was very nice, and the write-up was terrific.

I will say, though, having gone to all that work (either way), I would just spend the $50 or so (at Autozone) for a new switch, rather than trying to repair the old one or put in a used one.

props to you for figuring out how to unhook all of those cables to take the whole control panel out... there's not a lot of room there, and I didn't bother trying because putting it back in would probably be harder if I did manage to get them out

I just took apart the thing while it's still in the van.. it's not hard to get the fan switch out... mine was burned out too... it's usually the contacts inside the switch that gets corroded or oxidized and cause high resistance, which in turn burns up that pig tail... I found a good pigtail from the junk yard, cleaned and put a nice glob of silicone grease in it to keep those contacts from corroding too... swapped the pigtail out while I fixed my speedometer about 10 years ago... hope I won't have to deal with this again

[TheMAN]

its not the switch itself that scares me, its the prospect of replacing the harness. If I can use the jury-rigged wire to run off a good switch (which I probably have, in my 93) that would be somewhat less intimidating. Being nearly electrically illiterate doesn't boost my confidence.

then become "literate"... the shop manual teaches you how to read wiring diagrams.... if that's not enough, there's always different resources out there that can teach you... it's not that hard, you just have to think methodically and look at things one piece at a time instead of trying to absorb it all at once

[John Kaufmann]

... I went a different way, disconnecting all of the lever cables so that i could pull the HVAC control assembly and work on it. Your approach -- removing the switch without removing the HVAC assembly -- was very nice, and the write-up was terrific
props to you for figuring out how to unhook all of those cables to take the whole control panel out... there's not a lot of room there, and I didn't bother trying because putting it back in would probably be harder if I did manage to get them out

I just took apart the thing while it's still in the van.. it's not hard to get the fan switch out... mine was burned out too... it's usually the contacts inside the switch that gets corroded or oxidized and cause high resistance, which in turn burns up that pig tail...
It's precisely because there's not a lot of room that I wanted it out. I found it exceedingly hard to get the switch out in that small space. That's why I was so impressed with Jonny's write-up, showing in detail how he managed it.

The key to pulling out the HVAC panel was making a tool (https://www.toyotavantech.com/forum/showthread.php?7519-Removing-the-Previa-HVAC-panel) to disconnect the cables. Of course, having the panel out made replacing two switches (HVAC blower and rear defogger) a piece of cake. [My other reason for pulling that panel was that I was inspired by Dan (man_btc) to add seat heaters. That meant adding switches, one on each side of that center panel -
11128
- wiring them to the seats below and the fuse panel above. Having the HVAC panel out just made all of that easier, but it did require pulling up the whole dash panel. Having seen Jonny's post, I would try that if I had to do it again for just the blower switch.]

[Previologist]

then become "literate"... the shop manual teaches you how to read wiring diagrams.... if that's not enough, there's always different resources out there that can teach you... it's not that hard, you just have to think methodically and look at things one piece at a time instead of trying to absorb it all at once

Well becoming electrically literate and learning to rebuild motorcycle engines are both on my short list of things I never ever wanted to learn, and I'm already trying one of them this summer (against my better judgement).

[TheMAN]

desperate means needs desperate measures...hardly anyone wants to work on these vans, and if you're going to fix it right, you're going to have to force yourself to learn how to read wiring diagrams, like it or not

[Previologist]

The only reason I started rebuilding my motorcycle is because it was dead and would cost thousands to have repaired. It remains to be seen, if I ever finish, whether I've done any good or just wasted a few hundred dollars in parts.

Problem is I'm not desperate, because the blower isn't dead. As long as the blower works on high, I have heat and cold and therefore a reason to procrastinate. :wnk: Once I finish murdering my bike I will take a look back over this and related threads and decide if I want to proceed.

[Previologist]

Well the good news is I took my bike engine apart and put it back together and it ran afterward, though not very good, and I still need a new bike or new engine.

The bad news is the high power on my blower (which is all I had) has been acting up and not worked a couple of times. Naturally this happens 2 days before I have to drive cross country and need the a/c. Hopefully its just a minor connection issue and I can continue procrastinating on learning to read wiring.

Edit: Its the blower going bad. Hopefully I can keep rapping it back to life for one more week until I get back to my garage. If not it's going to be a very warm drive.

[Previologist]

Is there a strategy that would help keep my dying blower alive a few days longer longer, like keeping it on at all times versus using it little? Since this is a brush issue, I presume using it as little as possible would extend the brush life, but I'm also afraid every time I shut it off I won't be able to jar it back into action.

Probably a no win choice, huh? :cnfsd:

[John Kaufmann]

Wayne, in the course of this thread - over many months - several people, based on painful experience, have said your symptoms sound like the blower switch. I have seen no indication otherwise. That does not mean the problem is not the blower, but please remember that people take precious time to share their experience because they want to help. (Get-help/give-help is the way these forums work.) At some point, after seeing that their suggestions make no difference, there is a natural tendency to feel that time spent was wasted, so people give up trying to help. Sorry.

[Previologist]

This is a new problem, starting 2 posts ago John, I just tacked it onto this existing thread. My googling tells me its a brush problem. The blower stops working and I have to give it a smack on the side of the housing for it to start up again. Sorry I thought I was being more clear about that.

Don't think I'm not grateful for the advice on the original problem just because I haven't addressed it. One must choose one's battles and that's just not one I've been ready to tackle, especially since the blower worked fine on high until the brushes started going out.

[Jonny]

With nicer temperatures coming up soon in the Fall, those couple of months would be an ideal time to fix all the blower system problems prior to the arrival of Winter. Your vehicle has had plenty of battles from which you have had to choose, and this just might be an important one to not put off too much longer. Fix the blower motor first to eliminate that problem item under the hood, then start dismantling the dash to get to all the wiring and the switch. If the dash and wiring part of this fix is intimidating I am willing to dismantle my dash and take pics to post on here as needed. However, my van is parked on the street and after Nov 1 you'll be SOL!

[Previologist]

I appreciate the offer but wouldn't want you to go to that much trouble quite yet. This chore is on my radar, but it's on the "to do, if I find time and feel up for it" list. I've been away from home and garage for almost a year so ahead of it on the "Must Do" list now that I'm back are things like stain the deck and as much house as possible, other outdoor chores, possible timing chain on my 4runner, and more. I will at least use the good weather season for attempting to take the switch out of my parts van (if it works), and if I can get that done it will be a step forward and I'll have a better idea what I'm getting into. Its the wiring part that bothers me more, but maybe once I get at the switch it won't seem so bad.

OTOH over the 20,000 miles and 2 years I have on this van I've found very little need for multiple blower speeds. The lowest speed on Previa blowers does almost nothing and wouldn't be missed by many, and adjusting the vents and temperature control accomplish much of what I have ever needed.

I definitely have to replace the blower though and I have to see what the previous moron did to my blower housing, which doesn't even close all the way. I wouldn't be the least surprised if he installed the wrong blower or something equally idiotic.

[Previologist]

Pulled the switch from my parts van which was pretty simple because the dash is partly disassembled already (except for finding that one screw that holds the switch in because I was looking underneath, not above the switch). Got it out and...yay...it does work but it shows obvious signs of overheating, and even has a small crack there. But I've seen worse, and maybe when I pull the one from my 97 I can patch together one unscorched switch. Otherwise I'll just use it until it breaks.

The real elephant in the room is the harness. I will have to remove the driver side kick panel or whatever you call the panel under the steering wheel to even see where that goes before I decide if its something I want to tackle. I suppose creating all new wiring from the switch is an option too, which sounds equally unappealing to an electrical incompetent. But first things first. I'll see if I can trace that harness in the parts van.

[Previologist]

Things are looking up. Got the blower and housing pulled from my parts van, and now that I can see the whole situation on that one I have renewed hope for a happy ending. Since the clown chopped the blower wires off AFTER the blower assembly connectors, unless he did something clownish between the connectors and the dash switch that I just can't see yet (and that seems unlikely), it should be fairly simple to wire it up for all speeds again...In fact I can probably just install the entire blower housing, resistor and harness from the parts van as a unit and just plug her in. Or so I hope. Will be a bit before I get to that job but hope to have this all done by the end of October, if not sooner. In the middle of a major garage overhaul that needs to be done first.

[Previologist]

Surgery is underway...I pulled the blower from my 97 and found the main harness and blower connectors intact! :dance2: I plugged the 93 blower into it and have all speeds except high. Not sure why, because high worked when I tested it in the 93, and high worked on the 97 (if I banged on the blower housing) before I started but will see what happens when I try changing switches. Its running through the (93) resistor now, but doesn't high speed bypass the resistor?

Correction: It does blow on "high" but I could barely hear it from the cab because it is actually blowing at a similar speed to the lowest setting. Maybe its just because the van isn't running? Anyway this is a better problem than I had before. :LOL2:

Edit: Nope, the same when its running.

Edit #2: ahh, looks like the 93 has a different blower. Weird, but I wonder if that's the problem or not...:cnfsd:

[Previologist]

the blower motors appear identical except for how they are designed to mount in the plastic housings, which are configured differently from 93 to 97, so even though the blower seem to be the exact same blower they aren't interchangeable. I opened up the 97 blower and found one of the brushes was totally shot, as expected. So I just lifted the entire brush mechanism out of the 93 blower, and put it in the 97 blower. I wanted to bring the entire innards over, but couldn't see how to get them out. I didn't take the squirrel cage off, and that might be be why it wouldn't come apart.

Switching brushes gave me high speed fan back again. But this must mean the missing low speeds problem is in the 97's blower itself, which doesn't make sense. But it doesn't matter.

Anyone know how to get the entire innards out of a blower motor? If not I have will to order a new one. I thought I might be able to just slip the 93 blower and its plastic housing right in to the 97, but there is a slight configuration difference with how they mount too. The 2 bottom screws are spaced different.

The good news here is that I don't think I need to mess with my switch at all, yet, since I have all speeds (sort of) depending on which blower is hooked up

[John Kaufmann]

... I plugged the 93 blower into it and have all speeds except high. Not sure why, because high worked when I tested it in the 93, and high worked on the 97 (if I banged on the blower housing) before I started but will see what happens when I try changing switches. Its running through the (93) resistor now, but doesn't high speed bypass the resistor? ...
Yes, using the contact of the Front Heater High Relay.

[Previologist]

That's what I thought. Sometime after I tested the 93 blower in the 97 and it blew very weakly on high setting, I had a suspicion that I had not hooked up the connector that goes directly into the blower. I may have only hooked up the 2 connectors that go to the blower subharness. If I'm right, could that be why the high setting only blew very weakly?

It doesn't matter though. I apparently have to buy a new blower anyway. Thinking of trying the cheap VDO blower.

[John Kaufmann]

... Sometime after I tested the 93 blower in the 97 and it blew very weakly on high setting, I had a suspicion that I had not hooked up the connector that goes directly into the blower. I may have only hooked up the 2 connectors that go to the blower subharness. If I'm right, could that be why the high setting only blew very weakly? ...
I wouldn't know. According to the EWD p.144, there are connections from the blower to connector IE2 and from the resistor to IE3. [Connectors IE1 (A/C clutch), IE2 (blower) and IE3 (resistor) are tucked up in the cabin side of the expansion valve. (p.24)] According to p.148, the nominal ohm values for blower series resistance are:


0 (HI), 0.48 (M2), 1.42 (M1), 2.34 (LO).


Of course, that requires both IE2 and IE3 connected; if only IE2, you could still get HI speed, but no lower speeds. If slow on HI setting, that is not a matter of something not connected, but of a high resistance (>2 ohms) in the connected circuit. How you could add a few ohms to that circuit? The blower is possible, of course, as are any connectors, but the most common source of a few ohms would be a scorched switch contact.

[Previologist]

It blew full-on high with the old fan with different brushes though. I guess the mystery will be solved, or become irrelevant, when my new blower arrives. If that one blows soft on high then I'll have to excavate the switch. Here's to hoping that doesn't happen, although its not that hard to get out.

[Previologist]

well the VDO blower was a mistake. :no: The mounting holes are off by a fraction of a mm, I can get them all on but one. Since I'd void the return policy if I enlarged the hole, back it goes for a 4 seasons...

[Previologist]

VDO might have been a blessing in disguise. I was messing around with it and my other 2 when I realized that although the 93 blower mounts and connector are oriented completely different, the 93 does actually fit in the 95 housing. So tomorrow I test it again, making sure to hook up all the wires this time. I may have to lengthen the wires that go directly to the blower because that connector now ends up on the complete opposite side of the housing.

Also I don't know if that little hose that comes out of the motor is an air intake or an exhaust to blow out brush dust, but I had to tape the 93's to the 95's hose so it would reach the fitting. Not sure how important that is, the VDO didn't even have one. Getting the cage off the VDO with scratching it oughta be fun

[John Kaufmann]

... I don't know if that little hose that comes out of the motor is an air intake or an exhaust to blow out brush dust, but I had to tape the 93's to the 95's hose so it would reach the fitting. Not sure how important that is, the VDO didn't even have one. ...
The hose is just for air from a point cooler than the motor itself.

[Previologist]

It should work fine then.

But I'm back to maximum confusion. This 93 blower worked on 3.5 speeds when I plugged it in using it's subharness. But that housing won't work, so when I put it in the 95's housing with the 95's suharness, it only worked on high. :no:

I guess now I need to see if I can switch the subharnesses. :cnfsd:

[Previologist]

It should work fine then.

But I'm back to maximum confusion. This 93 blower worked on 3.5 speeds when I plugged it in using it's subharness. But that housing won't work, so when I put it in the 95's housing with the 95's suharness, it only worked on high. :no:


Duhh, that's because the 95's connector to the blower was decapitated (lower picture in post #6) when they ran the wires direct from the front heater relay (upper picture in post #6). So when I use the 95's harness, the resistor is bypassed and I only have high from the direct wire from the relay.

But since high works in that scenario, the reason it only blows slowly on high when using the 93 subharness can't be the switch, if my reasoning is correct. Let me know if anyone disagrees. Because I'm thinking of cutting my losses and wrapping this up, and just settling for 3 speeds. I don't see any reason a new blower would behave differently, so it seems I'm stuck with either high only, or a 3 speed fan with no high. But I save 100 bucks.

I suppose one last thing I could try, and it would be a crapshoot, would be to splice my 93's blower connector into the decapitated wires, and try that. I checked and it does have power.

It would make absolutely no sense if that works, because why would they have cut it off then? But its easy enough to try. Tomorrow. or another day. I'm as sick as anyone of this 2 year old thread but I also don't like being foiled!

[Previologist]

Eff it. I'm going for the switch.

[Previologist]

Things are "heating up"...

11783

That right side contact with all the greasey goo on it is the HIGH setting of the switch...so I'll formulate a theory that is probably wrong, but any parts that are right can be credited to John and the others.

Because of the dirty high contact, and additional resistance from other connectors in the OEM wiring harness (at least 8 connection surfaces, 2 per connector), there isn't enough juice to fire the blower at high speed on the high setting. But when using the direct wire from the heater relay, it has less resistance and the blower works on high.

Actually that sounds reasonable. Now to clean this up, add new dielectric grease and put the theory to the test.

[Previologist]

Welp...it seemed like a good theory. But it wasn't. I cleaned up the copper in the switch, di-greased it again and still only low speed on High. I tried the 93 switch too, same.

So in summary:

When I got the 97 van it only blew on high. PO had rigged a wire directly from heater blower relay, bypassing the OEM sub harness and resistor pack

The PO had cut off the harness connector to the blower, in favor of the above direct wire.

When properly wired with the 93's harness the blower only works on 3 speeds. On high it blows similar to low.

The blower worked on high in the 93, and will blow on high if using the direct wire that was rigged by PO from the high blower relay. So it's not a blower problem.

I hear and feel the heater relay clicking when I switch to high. There is a slight delay-if the AC is on the AC light will go off for a second until the relay clicks and delivers power to the blower. That may be normal or irrelevant, I dunno.

I've tried multiple resistors, including brand new and the one that worked fine in the 93.

The switches both check out. The 93 switch worked on all speeds in the 93. Although there were signs of mild overheating in the plastic of both switches, I see no scorching of connectors anywhere, and I cleaned up any minor discoloration bringing shine back to the copper.

The only thing left I can think of is to check all connectors again and then, last gasp, try splicing another blower connector into the 97's harness but I can't imagine that will do anything. And I suppose if I was sure how to go about it, I could check resistance between the blower connector wires and the switch connector. But since they are on opposite sides of the firewall, I think I can forget that. Maybe check the voltage in the decapitated wires on different speed settings?

Just talking to myself to organize my thoughts.


EDIT: So I checked all the connectors (look good) and checked the voltage on the cut connector wires. I wasn't getting consistent readings, but it was under 12 on all 4 settings with engine off, with high only marginally higher than medium, and mid-14's on all settings with engine running. I spliced a connector onto it and lo and behold! No change. Still no high.

So I think one mystery is solved-they wired the blower directly because this problem exists, and like me, couldn't figure out the cause. It must be either in the wiring between switch and blower housing subharness because it was the same with my other blower housing subharness (and which means it will be nearly impossible to access and fix without tearing the entire dash apart), or if the computer is involved maybe its a problem there.

But unless anyone has new ideas, I'm done here. I just have to decide if I want a blower with 3 speeds and no high, or a blower with high only. I think it will be the latter. Many thanks to all who tried to help so far, or if you have any last gasp ideas.

[man_btc]

[edited - screwed up the first time - my apologies]

I agree you probably have a harness problem - your broken connection is probably between:

the switch's "High" contact pin 8 and pin 4 of the "Front Heater (HI) Relay." - so the HI relay coil is never energized (do you hear/feel it click?)
-or-
the motor pin 1 and pin 2 of the HI relay - no path from the motor to ground when that relay is activated. I'd consider this the most likely, since it carries significant current.

(The HI relay's ground (pin 1) and ignition-on 12V (pin3) are from solid bars running underneath the relay socket on the underside of the fuse panel, so there's almost no chance those connections are broken)

As described in the earlier post containing the schematic, the fan switch does two things - once it's no longer in the "off" position, it grounds the coil on the "Front Heater Relay" - so that relay closes and applies voltage to the "+" side of the blower motor. Along with that, the switch also controls the current through the motor by setting the resistance to ground from the "-" side of the blower motor:

- Low speed (shaded bar on the schematic one step to the left, with no connection to the resistor block) = low motor current flows through the entire resistor block to ground (via the "W wire)
- Medium and Medium-High speeds (shaded bar one or two more to the left; switch pins 1 & 2) = sets shorter paths/lower resistance through the resistor block to ground, so more current to the motor
- High speed via a direct motor-to-ground connection through the "Front Heater (HI) Relay" when its coil is grounded/energized by the fan switch in the High position (shaded bar all the way to the left); therefore the highest motor current

If that last connection - the direct path from the motor to ground via the HI relay - is broken, you wind up with the same current path as Low Speed (fan motor pin 1 all the way through the resistor block to ground). That could be because

- the relay itself doesn't work (which you ruled out)
- it isn't activated because there's a break along the path from the switch contact pin 8 to the relay coil pin 4
- the relay closes but the connection to pin2 from the fan motor pin 1 isn't there.

A possible alternative to fixing the harness would be to either

-install a manual switch to bypass the fan switch connection & apply ground to Pin 4 of the HI relay to trigger it
- or -
- placing a manual switch from the fan motor pin 1 (via that blue wire that was added?) to ground. To get High speed, you'd have to turn on the fan speed switch to anything other than Off, then flip your extra switch to bypass the resistor block. In both cases, the original harness would be reinstalled to give you the lower speeds.

[man_btc]

and of course I'm talking going with the original harness to the fan housing

[man_btc]

Maybe this helps?

[Previologist]

Thanks Dan. I'll have to study this a bit. It makes sense but I want it to sink in more.

Perhaps ironically, in a somewhat parallel situation my 97 4runner has a ground issue too but its in the engine running circuit. It has a software ground that apparently went bad, and it would start but would shut off immediately. With help from someone on another forum I rigged a physical switch to ground to bypass the computer ground.