Alternator not charging, but alt is good

[Tercel__jon]

So this one has me confused.

The 83 sat for 3 months, I fired it up yesterday, replaced a few things (steering Ujoint and window crank) and when I went to drive to the gas station today, I heard a pop and my alt light came on.

Took the alternator in, and it checked out. I swapped in the brand new looking voltage reg from the parts car, still nothing. I checked all my fuses and found my "engine" fuse was popped. Replaced it, still nothing. Dicked around with the wiring, made sure all my connections were good, fired the car up and still nothing, but when I went to shut it off, the "engine" fuse popped again.

Im completely at a loss right now, and theres a huge snow storm on the way...

Ive been contemplating throwing this random GM 1 wire on there to get me through the storm.

[Tercel__jon]

Upon further investigation, I have power with key on going to the voltage regulator, but nothing coming from it to the plug on the back of the alt. I know one of those is the exciter wire...all three show 0.00 volts.

[Mark]

The first thing I would do is check the wiring from the alternator and the distributor to see if there are any loose/corroded/damaged wires. Also from looking at the wiring diagram in the factory service Manual on this site, it looks to me like if the voltage regulator on the alternator failed and the alternator was putting out too much voltage, the 15A engine fuse could blow. It sounds like you have the external voltage regulator (if you replaced it separately)? Maybe the replacement voltage regulator is defective or the wiring to/from it is the problem. I don't think I've ever had a car with an external voltage regulator so I don't have any experience with them.

[Mark]

Upon further investigation, I have power with key on going to the voltage regulator, but nothing coming from it to the plug on the back of the alt. I know one of those is the exciter wire...all three show 0.00 volts.

To me (again looking at the wiring diagram), it almost looks like the excitation circuit won't be supplied power from the battery if the 15A engine fuse is blown. You could start the car with a new 15A fuse and if it doesn't blow for long enough, check the voltage at the battery. If it's much higher than 14 volts (I once had 17 volts on my old Camry with a failed regulator) that could be your problem. If the battery is showing around 13-14v at a variety of engine speeds, when you turn the headlights on/off, etc, then I would guess the voltage regulator is fine.

[Tercel__jon]

True. Ive traced the black-red wire from the 15a engine fuse to inside the body, then it comes back out to the regulator.

Well, It only goes to the emissions control computer, then comes back out. I pulled the ECC and its STILL popping. So Im gonna just cut it where it goes into the body and bypass whatever it does in there. It just needs to go to the regulator somehow.

Not like the emissions control computer is used....4a swap with full vac delete and engine bay all cleaned up

[Mark]

The wiring diagram shows the wiring from the 15A fuse going directly to the voltage regulator with a separate wire (with the same wiring colour) branching off and going to the emissions computer.

wiring 1.jpg

wiring 2.jpg

[Tercel__jon]

I traced it to the emissions control computer inside the car then coming BACK OUT to the regulator. So I just cut it where it goes in and comes back out and its FIXED. It works and Ive got 14.5 volts. Im happy.

It only ran to the emissions control computer, then back to the regulator. That comp is useless, so yeah. Bypassed it and whatever short was in the harness.


Oh, and yeah, I have that same diagram. haha. Had it spread out on the bench the entire time.