Last summer I upgraded to the 145amp truck alternator and it had been working flawlessly, easily keeping up with my sub amp. I recently started a Procharger install, and when I got everything hooked up, my alternator stopped working.

Well, this is pissing me off. I actually have two truck alternators because last summer, the first one I bought off ebay didn't work when it showed up. I mounted it, started the car, and the voltage never moved off 11.8 volts. So I reinstalled the factory one, contacted the ebay seller, and he sent me another truck alternator, and that one worked. The seller didn't want me to send back the other one, so I stuck it in the basement.

Fast forward to this weekend. Got the procharger back up and running and the alternator isn't charging. So today, after work, I went to Pep Boys and had them check both of the truck alternators that I have and guess what, both alternators checked out fine.

So on the ride home, the only thing I thought it could be was the actual mounting of the alternator in the bracket. I was thinking that by going to the studs for the procharger, and not having that back mounting bracket, maybe I wasn't getting a good ground.

So I got home and cleaned up the mounting locations with a file, and mounted one of the alternators, crossed my fingers and started the car and nothing, voltmeter off the back of the postivie terminal on the alternator reads 11.8 volts which is the battery's voltage. So my next step was to add a grounding strap from the case of the alternator to the frame and still nothing.

So now I'm really f'in perplexed. I've got two alternators on my workbench that supposedly both check out fine, but I can't get either of them to work. What's next, the exiter wire? I checked that on Saturday and with the motor off, and the key on, it gets 11.8 volts, again, the same as the battery.

So does anyone have any suggestions? I'm eager to the car back together, but without a charging system I'm not getting far. Is there a fuse I need to check? I'm annoyed right now, and trying to backtrack everything I've done to make sure I didn't f something up.

 

Just an update that might help... I scanned the car and I have a P1637 code, Generator L-circuit. I cleared the codes, and within 30 seconds, it comes right back. What's the best way to check it? Unplug it and check the voltage?

 

First, I'd check the pins in the alternator's connector shell. If they're all snug and making good contact, then look for a crimped or broken wire coming off that same shell...

 

I will do that tonight.

I've had that P1637 code for a long time and never had issues with charging, so I'm not sure it's related.

I might pick up a new exciter wire harness just in case. It's cheap insurance to eliminate it as a suspect.

 

Exciter wire would be the first place I'd look...it is thin and easily broken.

 

But if I unplugged the harness, and tested it with a voltmeter, wouldn't that give me an indication of it's functionality?

 

That would probably tell you what's going on, but I'd still trace that wire and check for any chaffing along the way back to the PCM.

 

does the test bench tell what volts the alt was putting out?

 

Yes, a low of 13.5v and a high of 15.0v. Both alternators tested out the same, which I would expect to see.

 

It turns out it was the exciter wire harness. The metal plug inside it was compressed to the point that it wasn't making contact with the contact on the alternator. I used a jewler's screwdriver to pry it back out and started the car back up and the volt meter went up to 14.8 volts.