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  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
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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
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    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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    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
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    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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    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

  10. #10
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    Re: Incompatible alternator/ harness...

    Actually, there have been three different alternator HARNESSES for the vans: 1984, 1985, and 1986-89. All are now NLA. The differences in the harnesses have nothing to do with the connector to the alternator itself, but rather other connectors included in the harness. 1984 has no oil level sensor wire because there's no oil level sensor. 1985 has oil level sensor wiring connectors that only mate with the 1985 (3Y) oil level sensor AND the corresponding oil level sensor wire in the 1985 chassis wiring harness. The function of the wire is identical to the 1986-1989 oil level sensor wire, but the connectors won't allow the harnesses to interchange without splicing in the appropriate connectors (guess how I learned ).

    The alternators themselves are totally interchangeable and the same for all years despite part number supersessions.

    I'd get a Denso (or rebuilt Denso) alternator. Even if for some bizarre reason the harness on your van has been molested and has a nonstandard connector, a spare alternator is always a good thing to have on hand.

    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")

  11. #11
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    Re: Incompatible alternator/ harness...

    Quote Originally Posted by TheMAN View Post
    According to Toyota's reman guide, there's 3 different alternators used in these vans, depending on manufacture date....

    This is true, however all 3 of these alternators are 100% interchangeable. There are slight internal changes. The earlier ones are rated at 60A and the later ones are rated at 70A. Tim

    PS: Thanks for sharing that guide with us

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    Re: Incompatible alternator/ harness...

    www.rockauto.com has these for a much more reasonable price than Toyota. The only difference is you won't get the box that says "Toyota"


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    melted alternator plug, anyone got an extra on they could snip?

    okay so this looks like the fault of accumulated psf. thought I had fixed the leak with a new hose but i guess there was still a small drip.

    anyone got one of these they could sell me or any crafty ideas.
    Thanks, Niko.





  14. #14
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    Re: melted alternator plug, anyone got an extra on they could snip?

    The harness for the van has been discontinued, but there are lots and lots of similar harnesses on other models in the salvage yards. You could chop that end off of one then solder/shrink tube it to your existing harness. For an emergency repair you could do what I did (below). The spades inside the alternator are standard so you can make each connection individually (just don't mix them up). Tim


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    Alternator Wiring Pigtail Connector

    I replaced the alternator pigtail connector on my 89' 2WD van with one I found at the salvage yard that was on a 88' Camry. It fit just fine but the wire gauge was smaller and the wires were different color. I may have spliced it on incorrectly. I want to take the pigtail connector off and use three clips instead but need a diagram that shows which wire connects to where. Can somebody please help?

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    Re: Alternator Wiring Pigtail Connector

    Here's a diagram I marked up with the wire colors used on van harnesses:


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    Re: Alternator Wiring Pigtail Connector

    Wow! That's perfect. Thank you so much.

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    Re: Alternator Wiring Pigtail Connector

    Quote Originally Posted by timsrv View Post
    Here's a diagram I marked up with the wire colors used on van harnesses:

    My charging wire (+box to the alternator post) is actually two 10g-ish wires with separate eye connectors to the alternator post. Can someone please confirm that this is the stock setup and not something shady from the PO? I discovered (after much popping and smoke until I unhooked the batt ground) that indeed a 2nd wire (with a missing eye connector) was partially exposing itself out of the harness sleeve. I'm frustrated I didn't catch this earlier, and am concerned that I may have fried a thing or two as a result.

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    Re: Replacing the alternator harness

    Pos box should have 2 wires with ring ends.
    One heavy wire coming from the battery, the 2nd heavy wire goes off to the alternator.

    The factory wire is fairly light gauge and I dont remember if it was a double wire or not.
    When I replaced mine I used 8g wire with soldered ends.

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    Re: Replacing the alternator harness

    Thanks, Burntboot. Looks like mine is similar to Ratatouille's in post #44 (likely 10g and a second 12g or 14g wire). But since the repaired wire is now a tight fit and I foolishly broke the +box in the process, I'll be upgrading to an 8g this weekend.

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