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Hi-
My 1991 Toyota Previa's A/C just stopped working. I was told that it is a temperature control switch that is located deep in the dash. Is this true? I just had the expansion valves, blower fan and compressor replaced. Now the blower fan stopped working I was told that it is a temperature control switch that is recessed deep in the dash. For some reason I think the mechanic lied to my wife. Could someone tell me if this switch exists?
Sounds like BS to me. I could be wrong, but I'm not aware of any such switch. Does the fan work for heat? If the fan doesn't work at all, then I'd check the circuit breaker 1st then I'd check for power at the fan motor. If there's power to the motor and it's not turning, then you have a bad motor. If the motor doesn't have power, then I'd track the circuit back-wards. Other likely causes of failure could be the heater relay or the fan switch on the dash. There's also the blower resistor, but if that failed it would still work on high. I need to go on a job right now so there's no time to review schematics or post pics. I'll come back later tonight or tomorrow and give you a more thorough response. Tim
Okay, I took a picture and marked it up. Pull your fuse cover (top of dash) and locate your front heater circuit breaker. There is a little hole in the top of it. This is your reset button hole. Take a pen or something small and pointy, stick it in this hole, and give it a push. If you hear a metalic click, then the breaker was tripped and you just reset it.
http://i8.photobucket.com/albums/a23...l/IMG_0311.jpg
I'm guessing it's not tripped, but it's a quick and easy thing to check, so it's a good place to start. If it was tripped, then you gotta wonder what tripped it. Sometimes these things just trip for no appearant reason, but most of the time they trip due to a shorted motor or a pinched wire.
If the breaker wasn't tripped and the motor didn't have power, then the next thing to check is the relay. These relays rarely fail, but they can and do. They are pretty easy to test, but 1st check the other stuff and report back. I'd rather lead you down the right path based on what you find than to spell out every possible scenario. Tim
PS: If you do end up needing to pull apart the dash to access the fan switch, HERE is a good thread that will get you started. Tim
Hi Tim-
Sorry for responding so late. Okay, I checked the circuit breaker and it was okay. The fan still doesn't turn on however. I actually replaced the motor two months ago and the fan worked for about a week, but it would only work on high when it did work.
Since you replaced the motor I would suspect it's okay, but don't take it for granted. Get your volt meter out and verify voltage (or lack of it). Working on only the high speed would suggest the resistor (inside the heater motor housing under the hood), but these fan switches are also known for being a bit weak. At this point you will need to use your meter to track it down. Good luck. Tim
Quote:
Originally Posted by timsrv
Hey Tim
same problem here, blower only worked on certain speeds, replaced relay and resistor, not circuit breaker. I put 12 volts directly from battery to fan and fan purrs. No power at fan plug in. The ac light comes on with switch at all settings and I can hear the speed switch click between speeds if that means anything. Any tips? How can I check circuit breaker or other areas, I do have a good fluke. Thanks
PS Motor swap worked great, I used the 2 by 10 bolted to jack with strap approach
Donny
So when i remove the circuit breaker the ac light goes out and using my volt meter I get over 12V same thing with removing relay but I'm just plugging my volt meter in random slots. After putting them back in ac light comes back. Still no power at fan. Fan works when plugged into battery.
Any tips would be appreciated thanks , new resistor and relay. 93 previa
I just scanned my the front fan circuit in my factory service manual. Based on what you said I'm sure the circuit breaker is okay, but not entirely convinced the front fan relay is. Using this diagram you should be able to troubleshoot the circuit. I suspect you will find a burned connection somewhere in the circuit. Tim
http://i8.photobucket.com/albums/a23...ps2d5f7ea1.jpg
this might sound stupid, but I'm willing to bet it's a bad switch... the fan switches in old toyotas are all crap... my mother's corolla did the same thing but I was able to fix it by sanding off the melted plastic and cleaning the contacts
https://lh4.googleusercontent.com/-W...0connector.jpg
https://lh6.googleusercontent.com/-L...%20switch1.jpg
https://lh4.googleusercontent.com/-q...%20switch2.jpg
taking out the switch is a huge pain but not impossible... you first have to remove the entire center stack... radio out, register trim out, etc...
loosen the screws to the HVAC control switch panel and then push the support tabs that fit around where the radio goes and force it down as far as you could...
carefully remove the little rubber retainers that hold some of the cables in place and pull some of the cables off... do not take off more cables than you need to give you some more working room
you'll want to pull off the front panel... it's clipped on... remove the huge clear plastic that distributes the illumination light behind it also
then you'll find some screws at the top to remove... you'll just have to feel for it and use a very stubby Japanese crosshead screwdriver... they're not too tight, so an improper stubby Phillips screwdriver works...
removing those top screws are essential as there are plastic covers that protects some of the levers and also the switch... you'll just need to look/feel to figure this out... take your time
once the covers are removed, you'll see that the switch can be disconnected easily because you can now see and there's extra room... then the switch slides off by pushing a tab
there is a jumper harness with connector that will most likely be burnt... you'll want to replace this too... replacing it is NOT easy... it's best that you take off the gauge cluster trim and gauge cluster to get to it because the other end of the jumper harness hooks up right at the corner of the gauge cluster... it's basically impossible to reach it while it's still in place without risking you snap some plastic
this will take you a few hours to do and figure out... it's best you practice at the junk yard since that is where I recommend you find the jumper harness and switch... you'll want to take apart the "new" switch and clean the contacts and regrease with dielectric grease... I would do the same on the connectors too even though it wasn't done so at the factory... anything for corrosion resistance!
when mine went bad, it was blower speed 3 that was flakey and didn't work right... eventually it affected 2... so 1 and 4 were the only reliable ones
you don't have to make this complicated, I'm pretty confident that this is what your problem is... my experience with these crappy switches tells me so... based on the symptoms you had described, it's pretty indicative to me of a bad switch because the switch has multiple contact paths and the blower works at some speeds... one of them controls the A/C relay (lights up the button too), and the others control the blower speeds and stuff like that... look in the shop manual and you'll see what I mean...
but, if the blower motor is going bad... taking the blower motor out to bench test won't be a good test anyway as jostling it around may have moved the motor brushes around to make it work again... when mine died, it worked upside down but not right side up! At first I was able to get it to work (when still in the van) by moving the recirculate/fresh air lever to do a "thump test"... it was the equivalent of beating on the motor as the flap is very near the blower motor... it worked until the brushes were too far gone.... oh and btw, taking out the blower motor isn't fun or easy either... beware of aftermarket blower motors... they don't run as strong as the toyota one, but it's quite a bit cheaper... they also don't come with the proper connector and they expect you to splice the wires... so best to rip apart the original motor and gank the connector to splice on
sorry I don't have any more pics than this, I was in a rush and too frustrated to even bother with pics when I was busy ripping the dash apart to replace the switch lol
I've had some speeds go out on fan switches, but never all of them at the same time. Can happen I guess, especially if the "power-in" part of the switch is the part that burns. That picture of the burned electrical connection is what I'd expect to find.....the question is where. The switch is a likely place, but there are others. Here's a post that should help pulling the dash apart: http://www.toyotavantech.com/forum/s...sh-on-a-Previa. Tim
there's several power pins for both blower control and illumination, but two grounds I think.... the fat one shared for the blower and the little one for illumination
I thought he said some speeds worked?
Oh yeah, just re-read and see he does indeed say that :doh:. I guess I got confused when he said he hooked the fan motor directly to battery/12v dc to test (why waste time doing that if some speeds work?) :cnfsd:.
plus, as I said... going through that much trouble to pull out the blower motor to test it won't fully confirm whether it is a good motor or not since jostling it around during remove could've knocked the motor brushes back into contact with the armature
still not finding why no power to fan or resistor, when its on and ac switch light on hand on relay you can feel it click going from off to low then you feel the next relay click when going to high. I am taking dash apart to replace dash board lighting but assuming since relay clicks they are getting power just not getting power to wiring under hood ( fan and resisitor.......
so not thinking its switch it self I meant to say , thanks for wiring diagram .
it does have new resistor and relays not new circuit breaker
..
Quote:
Originally Posted by beoutside
So fan started working sporadically . Replaced relay. And resistor then tested at fan, no power. Ac light on and can feel relay click with low speeds, high speed relay clicks at high speed. When jumped power directly to fan fan spins.
Quote:
Originally Posted by timsrv
So fan started working sporadically . Replaced relay. And resistor tested at fan, no power. Ac light on and can feel relay click with low speeds, high speed relay clicks at high speed. When jumped power directly to fan fan spins.
Quote:
Originally Posted by TheMAN
I think you're looking for a burned pin or a burned connection point somewhere. You'll need to check the harness at the switch to make sure it doesn't look like "the man's" switch/harness. I'd also unscrew the mounts to the fuse/relay panel and lift it up to check the underside. Tim
PS: There's also a Front Fan (HI) Relay. If this one goes fan will still run on lower speeds, just not high. I marked up the fuse panel picture to show it's location (right next to the Front Fan Relay).
Yes, if the motor is intermittent, bad brushes in the motor are a very real possibility. & like the man said, jostling or banging will often temporarily make the problem go away. When brushes wear out sporadic fan operation is one of the tell-tail signs. Are you sure there is no power to the motor when it stops? When testing for power at the motor, you should be checking for 12V at the motor wires (don't rely on a chassis ground, use the ground wire going to the motor). TimQuote:
Originally Posted by TheMAN
Thanks Tim
yes no power at motor wires or at resistor 12 v setting on my fluke ground at battery ,will check connections as you suggest.
Donny
Quote:
Originally Posted by timsrv
Found the problem. First everything checked out fine switch , circuit breaker, relays , the problem was there is a connector between the fan and fuse board located behind the cowling above the fan blower motor. I assume is was never fully pressed together and took 280000 miles to finally jiggle loose. When it first started going out and I would tap the cowling it must have been enough to complete the circuit and run. Then it finally loosened itself completely and no longer powered resistor or fan. Wish I would have worked from the fan back vs switch down.
That's one for the books and I now have spare relays and a fan motor :)
Donny
Quote:
Originally Posted by beoutside
Replacing all dash board bulbs ( LED) and heater panel ones as well anyways :)
Quote:
Originally Posted by beoutside
That's a relief I'm sure. I fixed a similar on my 86 van last week. Connection point on back of the fuse box burned. I was so sure it was a bad motor I had already purchased one to put in. Before I swapped it out I checked for power at the motor leads and found there was none. When I reached up to wiggle the heater relay it started running again. I popped out the fuse box and a close inspection of the back revealed a pin/wire that looked a lot like TheMan's picture of his switch connection. Fortunately I have a parts van and those parts were in good shape on that. Tim
awesome... I'm surprised you only found this out now... what did you do to replace the fan motor? I took the entire blower box out to do mine, which meant also disconnecting that sub-harness just above the evaporator
I thought it was a very bad problem because the front fan panel and the rear ac unit would not turn on. It was like it had no power. I then went to the fuse panel in the center of the dashboard and from there I checked the different fuses and I saw that the ac fuse was broken in the middle. The diagram of the fuses is on the center panel once the top is taken off. I replaced the fuse with the spare one in there and it worked good. The front fan and ac plus the rear fan/ac unit started working.
Quote:
Originally Posted by terbennett