Need Help ASAP With Alternator Problems

[chevyracer8262]

I have an 85 C10 swb truck with an 89 tbi injected 350. I've been having some charging problems. I tested the alternator on the truck with my battery charged/tester and one minute it's tests good next it tests fault what could cause this? On those alternators how does the 2 wires comming from the voltage regulator go to(1 brown and white, 1 brown)?

Thanks,
Chevyracer 8262

[Case 7230]

First things to check are the battery terminals. Are they clean and tight? Next check all the ground wire connections. It could also be worn/stuck brushes in the alternator. I assume the wires you are talking about go to the voltage regulator. It goes without saying that the drive belt is tight? The intermittant fault does sound like a bad connection somewhere. Some of the electrical experts may chime in soon. Good luck with it.

[chevyracer8262]

Well everything's grounded good because I just put this engine in this truck not 2 months ago and the engine wiring harness was pulled from the donor vehicle. All the appropriate grounds are hooked up and clean (I cleaned the all to the bare metal before I hooked them up. then coated them with paint). The engine has a 2/0 ground cable from the engine to the battery then from the same clean connection point on the engine to a cleaned spot on the frame also using 2/0 cable. This thing has grounds all over it. And yes the 2 wires are comming from the voltage regulator but are hooked up in the factory tbi engine harness. The alternator I'm using is a 105 amp cs-130 style from an 89 astrovan with the 4.3.

[bradrhale]

if it were brushes, it wouldnt charge at all. the unit may have a regulator problem. or it might be discharging prematurally. i have had an alternator that quit charging after so many rpm. if you throttled back out of it, she would start pumping juice again.

[03chevy]

if it has a external volt regulator then that is your problem. had that go out on my 84 honda prelude. but it will go out with a internal reg. too. sounds like that is your problem

[chevyracer8262]

It does have an internal regulator, and I've tried varing the rpm while testing the alternator and still comes back as a fault. Other the the charging problems the tbi injection system works great. I've tried bypassing the fuselinks directly to the battery with the same results. So I know they're not the problem.

[JOHN JAY]

Lift the battery terminal with the motor running if it dies then the alternater needs to be replaced or rebuilt.

[chevyracer8262]

I found the problem, the regulator wire was broke. Thanks, for all the info.

[bradrhale]

glad to hear it racer. guess that is why it was working part of the time.

[chevyracer8262]

I guess so, finding an article on rebuilding the cs130 style alternator really helped me out because it had a diagram and described how everything worked and the simple 2 wire hookup to make it charge. I found out these alternators are 105-130 amp and only require that the large terminal on back be hooked up to the battery and the L terminal on the plug be hooked to the ignition switch, everything else's automatic. So when I get my 396 put back into my Chevelle I'm going to be putting me one of these alternators on it.