yotayes88

Hey guys. so in the last 3 years or so, my 1988 toyota 4x4 has went thru 6 alts. 4 napa remans and 2 orielly remans. and i think my alt is about to die again. the brake/charge came on for about 3-5 seconds during a 100 mile drive today. it only happened once. but ever since i got the alt, if I'm doinng 45 mph and faster the headlights will dim out and get really bright. always random. so I'm pretty sure its a wiring problem. Where should i start?

wyoming9

iTrader: (1)

At the battery

You also want to look at your ground cables as well if these are the original ones it never hurts to upgrade to newer heavier ones.

Another place to look is at the B terminal of the alternator this wire carries the alternator output up to the fuseblock over the years from thermal cycling that wire just gets brittle and burnt.

Also the plug that goes into the alternator tends to corrode because of the location it is almost impossible to really look at.

When I get a Toyota of this vintage I always replace all the grounds run a new positive cable to the starter and the wire off the B terminal to the fuse block.

Just have your battery fully charged when swapping alternators

This should be a start.

yotayes88

I replaced the power cable going from battery to starter a couple years ago when i replaced the starter. I will replace the cable that goes from battery to engine block, because it looks old, and i haven't replaaced it since I've owned the truck. is 10 gauge wire big enough for the alt to fuse block?

wyoming9

iTrader: (1)

If I recall 8 gauge is what comes from the factory

If you didn`t know that wire bolts to the underside of the fuse block

Terrys87

iTrader: (1)

I would give the plug that connects to the alternator a good look over. I seen some in bad shape and you may need to replace it. I wonder if it is making good enough connection to run but not good enough to cause problems in the long run.

RAD4Runner

Yes, concur with above ^^^. intermittent connections would do that.

Wyoming is talking about the "Fusible Link" wire that screws directly into a fusible link module in fuse block here. Pic of whole wire is here.

Do not forget the "S" wire. Make sure it makes good contact with the "B" wire near the battery post, and that its terminal at alternator connector is good. "S" wire senses battery voltage, tells regulator to send more power if battery V is low, and tells regulator to send less power if battery is full.

Also make sure you have steady 12 V at "IG" wire (thin black and red?)

See "charging system explained" on my build thread for where all the test points are.

I recommend having a voltmeter with better resolution that stock so you can monitor battery voltage as you drive. I use . Should read between 13.5 and 14.5.

yotayes88

So i pulled the main plug off the alt, and i think i might have found the issue. All 3 wires on it are frayed/the coating is broken. they are still intact, but are very warn out. only problem is i don't know how i should fix it. they are worn out right at the plug. can i pull the wires out of the plug and repair them?

RAD4Runner

There is a tiny tab on each pin of the plug you push so you can push the pin out Toward the back of the connector housing. Need to either look at FSM or inspect under magnifying glass to find that tab. Then you can try:

1. Spreading crimp of pin out,
2. Re-inserting wire (this time stripped properly),
3. Recrimping,
4. Then solder.

Might be tough. May be better to find replacement connector with pigtails and solder to the pigtail.

yotayes88

Could i crimp a spade connector/female end or whatever its called on each of the three wires and hooj them up directly to the alternator? Or does it need the plug to operate properly ?

RAD4Runner

Electrically, yes, it would work.
However, I don't know if that would fit, and you might have high risk of shorting those three pins. You have to look at size of male pins in the connector housing on the alternator.

Terrys87

iTrader: (1)

Agree^^^ That is a tight fit and would most likely short causing bigger issues. I have replaced the plug from a boneyard in the past.

yotayes88

So i took my volt meter and the the volts are good with engine off and with engine running. even with brights, heater, wipers, and two 55w offroad lights on it was still above 13 volts. but as soon as i wiggled the main plug on the alt, the volts dropped. so i think i have the issue. going to pull n save this coming weekend to try and get one. The ones off 2wd trucks are the same as 4x4 aren't they? I can't remember

wyoming9

iTrader: (1)

Be sure to cut the harness as far from the plug as possible on the one your getting at the yard .

Remove the electrical tape to get more wire exposed.

If you can`t find one PM me I should have one but the cost of priority mail would be more then if you can find one local I am sure

RAD4Runner

Makes sense. Most likely the "IG" contact. It would be a good idea to pull the pins out of the connector housing and inspect for frayed wires, corrosion, etc. This way you're absolutely sure of what you're are fixing/replacing. Each pin as has a tab that you push a certain way to allow pin to be pushed out toward the back of connector housing. Need good light an possibly magnification for that.

YUP!

Best of luck.

yotayes88

I am almost certain my problem is the main plug. all three wires on it look like they are about to fall off. the coating on them is broken. the wires still have connection, but the are starting to break. I'm going to pull n save this weekend to try and find one. Are they the same connectors in 2wd trucks and 4x4?

yotayes88

Went to pull n save today and grabbed the plug. cut the harness about 10 inches from the plug and used but connectors to hook the wires up. then covered them with a wire loom/ electrical tape. I picked up an alternator from oriellys . i also got a starter because mine had a stripped stud that the battery cable hookks to and it wouldn't tighten down enough to where the cable wouldn't move around. its at 12.13 volts with everything off and 14.38 with motor running.

RAD4Runner

Sounds good. Just monitor it. 13.5V to 14.5v with alt running is typical. I like using the cigarette lighter socket voltmeter (search Amazon . Around $5.00

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