Hi guys, so I've got alternator problems. It's not charging my battery and I assume this means it's blown. I've got 2 alternators from the previous generation, these have different connectors and I'm wondering if I can rewire one of these to work in my 85' truck. I've got three questions:

1. Is there an external voltage regulator for the alternators in 85-92 trucks or is it inside the alternator?

2. How does one test to see if it's a voltage regulator problem or an alternator problem?

3. Has anyone rewired the previous gen alternator to work with the 85-92 trucks?


Thanks! I'm trying to go wheeling this weekend and would love to have my truck on it's feet. I've attached a photo of the connectors on my truck..

 

Yukon - on my 88, the regulator is inside the alternator, I can't speak for the pre-85 ones, but I'd imagine your 85 also has an internal regulator. If you have the FSM (I can send you some relevant pages if you need them), and a multimeter you can basically check out the entire alternator.

1. With a multimeter, the FSM has some steps on how to verify the rectifier.

2. Check to make sure your brushes have some life left, if not they are cheap and easy to replace.

3. I used some alligator clips, a spare brake light bulb, and an 18V drill battery to check out my regulator, it failed the test, so I swapped it out with one from a spare alternator, the spare regulator tested good.

Having said all that, if your regulator is bad, a replacement regulator is more than the cost of an entire alternator, so unless you just want to troubleshoot to know what is the problem, it really doesn't seem to be financially worth it.

 

85+ should be internal regulated Alts. If you are using any before 85 you will need to rewire and add an external voltage regulator. I would take off the alternator you have and take to the parts store to have it tested before you buy anything.

 

With the prints you can wire any alternator that fits in the brackets