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Thread: Replacing the alternator harness

  1. #1
    Administrator llamavan's Avatar
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    Replacing the alternator harness

    See THIS Library Article for step-by-step instructions on replacing your van's alternator harness.

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: Replacing the alternator harness

    Very nice posting and photos. I cannot believe I never realized what the + box was until now! I want to replace the high current wires going to the ground and wires going to and from the alternator with a larger gage cable, probably 0 gauge. I plan to have a company that specializes in making large gage cables make them for me because it is very difficult to buy small quantities of welding cable and the proper connectors. Do you know the length of the wire going from the alternator to the + box? Does the other cable at the + box go to the fuse link box by the battery? Any idea of the length of that wire? I think larger gage wire for those two spots and the grounds will tweek a few more amps out of the alternator and make things a little more reliable. I also plan to replace the fuse link wire with a 200 amp fuse (enclosed in its own fuse box) of the type meant for super high powered amplifiers. They cost about $20 for the fuse and enclosure. The fuse is only to protect the high current wire itself which why the higher rating and the higher rating means it has a lower resistance.

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    Administrator llamavan's Avatar
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    Re: Replacing the alternator harness

    + box to alternator = 23"

    Stay tuned for the other section (+ box to battery). I have to deal with that SOON.

    Do you happen to know offhand what the current gauge(s) for those positive and negative wires are?

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: Replacing the alternator harness

    Yes, the wire is 4 gage which is typical. I know the cable going from the frame under the battery to the engine ground is 24" I admit I am still trying to figure out the best place to put the new fuse block to replace the old fuse link. I really do not like the idea of having it exposed to salt spray even though it has a cover. The fuse cover is not gasketed or waterproof amd it is far too big to put in the battery compartment

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    Administrator llamavan's Avatar
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    Re: Replacing the alternator harness

    Thanks for the wire gauge info! Because I'm not in a position to completely upgrade that circuit, I'm sticking to stock for now ... and because I'm really suspicious that I'm going to be rebuilding that positive wire, knowing the gauge and getting wire in advance is going to save me a bunch of time.

    My measurements of the stock ground wire are 10" from battery terminal to frame and 27" from frame to engine block (just had to replace one of those — different van — with a good wire from a parts van; the original broke clean off at the terminal on the frame).

    Of all the compromises necessary to make the vans what they are, the battery location is my least favorite (yep, even trumps the P/S pump location over the alternator). Anything in that area is already far too exposed for my tastes. Let us know what you come up with for that new fuse box.

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: Replacing the alternator harness

    One of my other reasons for upgrading the wire quality is because my remote start will not work with the AC on because the voltage drops too much under this condition. The van starts perfectly for cold weather to allow preheating in the winter, but cannot precool during hot weather. With the AC on and power routed through a remote start relay the voltage drops so low the starter does not even click. I have to admit i really love the keyless entry and remote start during the winter when it does work. Mike

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    Re: Replacing the alternator harness

    Positive wire from battery to starter = 56" (4 ga)

    + box to the first (1.25) fusible link (NOT the "infamous" 2.0 fusible link that lives in the plastic box next to the battery and is vulnerable to corrosion) works its way there through the wrapped wiring harness; any replacement will have to be run outside that, and is dependent on the routing you chose to use. It's 8 gauge wire.

    Wish I could also say that one of those wires solved my van's problem. Nope.

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: Replacing the alternator harness

    Thanks for the additional info. I will be replacing that wire with a heavier gage someday soon, I hope. I just found a spool of left over 4 gage wire in my shop I can use, but I want to use heavier wire yet where there is now 4 gage. What was the problem you wre trying to fix in the first place? I don't think you mentioned it in this thread. Mike

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    Administrator llamavan's Avatar
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    Re: Replacing the alternator harness

    No, I didn't mention, mostly because I'm only now just getting back to it (and I'd like to say that's because other vans have been fixed, but it's actually because I'm waiting on parts and for PJvan to kindly vacate the carport and jackstands, so my choices of van jobs to undertake right now are somewhat limited).

    Skyler is cooking alternators. Broiled, baked, fricasseed ... he's gotten WAY too good at it; he can now do this just getting down the driveway to the gate. Hot alternator implies (to me) WAY too much resistance in the wiring, but maybe I'm missing something (quite likely — electricity and I get along best when we avoid each other), so I'm open to suggestions! Skyler also blackens his positive battery terminal. I disapprove. I'm going to try a different battery in case the positive post is guilty (probably should have done that earlier; it's over 5 years old anyway).

    Even though I see no evidence of problems in any of the wiring between alternator and battery, and I can't document any increased resistance in any of it, I'm going to just finish replacing the whole sheebang before possibly sacrificing my last spare alternator to Skyler's new bad habit. I told him if he eats that one, he's gonna go visit my pal Curt's auto electric shop and he's gonna stay there until he behaves.

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: Replacing the alternator harness

    Gwen,

    Actually it is the opposite: if the alternator is ALWAYS hot that means there is too much of a load on it or something approaching a short circuit, but not quite. Bad wiring, if it has too much resistance, will get hot where there is too much resistance. I doubt very much if the problem is from bad wiring from your description. I assume no fuses have been blown. Yes, the battery could have a problem and drawing far too much current causing the alternator to become toast. Best way to figure out the answer is to become intimate with a digital voltmeter... What is the battery voltage when the van is not running (should be 12.5 volts or higher)? What is the voltage when the van is running (at the battery posts, should be about 14 volts)? What is the voltage at the battery with the ground wire disconnected ((should be about 12.6 volts or so)? I also recommend making sure the positive wires at the positive battery post cannot touch the chassis if the battery moves, like when making a fast turn. Mine did and the electrical system had a heart attack every time I made a fast turn. I love making fast turns in the van... Turning the connector on the post a few degrees fixed that. I strongly suspect a bad battery, however. The voltmeter can shed lots of light on what really is going on. Is it legal to say here that Harbor Frieght has been having them on sale? I got a couple meters for only $1.99!!! and they are decent.

    Allergic to meters? A hydrometer will work just as well and costs about $5. A hydrometer measures the specific gravity of the electrolyte in the battery. Doesn't work if the battery is completely sealed. A fully charged battery in good shape will read above 1.2 for EACH cell. If only one cell is noticeably below the others then that is your problem. A low number (compared to the other cells) is a very reliable indication of a problem with that cell like a short. Shorts between the lead plates in older batteries is very common. The lead plates shed metal over time and build up on the bottom or create a short between the plates. When this happens you have a bad battery. Sometimes this problem can be fixed with a high powered battery charger that literally can blow up the short, but the such batteries are already on life support and ready to be replaced. I used to build lead acid batteries for experimental electric cars back in the '70s.
    Last edited by Omicronmike; 10-05-2010 at 04:19 PM.

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    Re: Replacing the alternator harness

    Well, the battery was long gone by the time I read your post; new one is sitting in the carport waiting to go in this afternoon. I'm sure it was depleted below normal level anyway since it had started Skyler multiple times without being charged.

    I actually LOVE multimeters, but I don't begin to use them effectively for a couple of reasons. One is that anything I ever do with electricity is not repeatable — I was the kid who couldn't get two wires and a good battery to reliably light a bulb back in whatever grade that was. So I've resigned myself to having to do everything a zillion times and trying to decide which readings are representative of reality (yes, an assortment of clips helps immensely, but those aren't always possible). The other is that the durned thing is in Greek (admit it, there's at least one Greek letter on every meter! ). Besides the meter itself not being self-explanatory, any instructional material I've found defines unfamiliar terms and then promptly uses them to convey unfamiliar concepts. Kinda like med-speak goes right over most peoples' heads even after it's explained to them because the meanings haven't had adequate time to sink in. So I've gone about teaching myself only a few basic functions by trial and error, and then using logic to test stuff. Works great with circuit boards and a functioning example; I used to be able to shame techs with years of schooling. Not so easy with vans, since even side-by-side there's a lot of traipsing and maneuvering and keeping doors from whacking bodies and sometimes getting identical (or any) access to a tight spot in TWO vans takes more time than I have available.

    Anyway ... an update after this afternoon's session with Skyler ... your post gives me hope!

    BTW, as another fan of fast van maneuvers, I'm definitely in favor of battery tie-downs.

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: Replacing the alternator harness

    Update:

    First, I managed not to digest that there are TWO fusible links in the wiring running between plus box and battery terminal. The first section of wire (leaving the plus box) is 8 gauge, not 12 gauge (original post has been edited to correct the previous misinformation ). The wire later reduces to 12 gauge.

    Second, it WAS the old battery frying the alternators (spendy lesson ). I did replace one ring terminal (at the plus box) because the outside of it was corroding (interior wire was just fine; I cleaned it up anyway before crimping on the new 8 ga ring terminal), but decided not to replace anything else based on Omicronmike's information above. With a new battery, Skylervan is back on the road, my wallet is about to be two-alternator-rebuilds lighter, and next time I have an alternator croak, I'll be checking the battery per the above instructions as part of the replacement procedure.

    I also bought a battery monitor that plugs into the cigarette lighter (this one was recommended by somebody-or-other on TVP); I actually paid less on amazon.com and there are probably other inexpensive sources as well. I don't know how the accuracy stacks up against testing the battery directly with a meter, but it bypasses my own "non-repeatable results" handicap, and I can see it will be advantageous for "casual" battery monitoring when driving and especially when traveling (with "stuff" packed in the van making battery access less convenient).

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: Replacing the alternator harness

    Wire Harness NLA just tried to order

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    Re: Replacing the alternator harness

    That sucks. A few weeks ago there was a guy on TVP trying to sell a new harness for $25 in the parts section. I wanted it & would have purchased but he didn't give any contact info (when we started TVT I lost my TVP PM privileges & last time I tried to post it said I didn't have permission) Tim

    Here's the post: http://www.toyotavanpeople.com/forum...p?f=24&t=10638

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    Re: Replacing the alternator harness

    BTW, as another fan of fast van maneuvers, I'm definitely in favor of battery tie-downs.

    Gwen
    Just curious... Ever try doing the J-turn in a van?

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    Re: Replacing the alternator harness

    does anyone know the type of connector (type, number, etc..)that plug into the alternator? not the postitve wire with the red plastic cap but the other containing 4 wires. The entire alternator harness is not available but the toyota dealer told me he can find me the exact connector that plugs into the alternator.

    Maybe some could take a close picture of it and show me on the forum?

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    Re: Replacing the alternator harness

    I just wanted to let know that the female end of the harness that plugs into our Van's alternator is the same as the ones in the '91 Corolla model, which I believe is the same for the Corolla's that have that same body style.

    The 3 wires from the harness from the Corolla are the same as in the Toyota Van ('84 model in my case). Maybe someone can save some money like I did in the yard by conecting that end of the harness to another good end. I didn' take the whole harness out from the corolla, since it was attached to a whole bunch of other wires and I didn't want to follow it, so maybe the other end of the harness fits into the Van also.

    My problem was that the wires going into the harnes's female end that plugs into the alternator of my Van were barely hanging to the plug with no wire slack for reattachment. Hope it helps!

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    Incompatible alternator/ harness...

    First. I've gleaned tons of info off this site and cannot say thank you all enough, especially Tim and Gwen.

    That being said, I've hit a little bump in the road. While replacing hoses and repairing sensors I drizzled a little too much ATF on the Alternator. I thought I had it clean enough, but apparently I didn't. I pulled the old one and bought a new one and tried to install it today.

    The problem is... The plug on my harness is 28mm (male) and the receiver on the replacement alternator is 26mm(female).

    Unfortunately, the old alternator is long gone already and I'm trying to decide whether to order another alternator which looks a little bigger (Denso) from napa or if the harness on my van is not OEM and I need to replace it too. My van is 25 years old this month!

    After my last go around with alternators (3 miss diagnosed bench tests) on my Honda I thought I was pretty thorough watching over this transaction, but the tester's pigtail must have fit into both alternators, because we checked new and old.... lesson learned.

    Here's the model I'm thinking about getting... http://www.napaonline.com/Catalog/Ca...592_0280386462

    I think I could be missing something simple...

    Thanks for any comments, Witty comments will be rewarded by a photo of the PBR ATF fluid guard I "fabbed" up and had mounted on the new alternator.

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    Re: Incompatible alternator/ harness...

    If the sockets on both alternators look the same & have the same configuration, then the connector should interchange. Are you sure it's clocked correctly? I guess it's possible there's similar looking sockets/plugs that don't interchange, but I'm not aware of any. If this is the case, then it sounds as if they gave you the wrong alternator. If you give me a brand name and part number I'll cross reference it for you.

    As you may have read from my previous posts, a new Denso alternator or an alternator rebuilt by Denso will likely outlast most (if not all) of the other rebuilds out there. So getting one of these isn't a bad plan. If you get 2 different alternators from 2 different sources and find the same problem on both, then it's safe to say it's a harness issue. That being said, if necessity dictates, you can always cut that connector off the harness and plug the wires into their spots using standard spade connectors. The harness connector is only there to make the connection easy and to make sure each wire goes to the correct terminal. If you go this route, you will want to be careful not to mix up wire locations.

    The only other thing I can think of is the alternator wire harness has 2 of these round plugs (one on each end of the harness). One is a female and the other is male. Make sure you're trying to plug the correct one into the alternator (although I can't imagine why the other end would be disconnected). Tim

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    Re: Incompatible alternator/ harness...

    According to Toyota's reman guide, there's 3 different alternators used in these vans, depending on manufacture date... you can always buy one from toyota and be done with it... not cheap though... it's $173 + $30 core charge
    https://www.toyotapartsandservice.com/remanguide.pdf

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