The Stovebolt Site Forums The Shop Area The Electrical Bay Charging issues.... Update!

Okay, this cropped up yesterday on my '71. I have had issues for a while, it's getting worse now.

Truck is a '71 C10 w/ a stock 350. Externally regulated alternator. Both alternator and voltage regulator were replaced over the summer. Wiring is good. Clean wires, no splices and I just rechecked the wiring today.

Symptoms started out as thus: At idle the ammeter was in the middle, little above half. Turn on the lights, heater fan, or wipers and the needle would drop and then all of a sudden the regulator would open up and the needle would swing way over. Once it stopped charging the needle would drop to the discharge side again and the cycle would repeat itself.

Now, it has gotten to where the swinging is gone. The needle sits the same as it did before at idle. It does come up a little when revving the engine. However, now I turn the lights on and the needle drops to the discharge side and stays there, no swinging up anymore. Last summer I did a voltage check after replacing the alternator and regulator and it was running 14 - 14.5 at both alternator and battery. I just checked it this afternoon and it's running 12 - 12.2 at alternator and battery at idle. If I turn the lights on and check the battery side I can watch it go from 12.2 down to 6.00 and back up.

So.... I'm thinking I have an issue with my regulator. Sound right or am I missing something?

Could be a bad ground, either at the regulator or the the alternator itself. Otherwise, I would say the regulator is at fault. You should be getting around 13.5 at idle.

Sounds like a bad diode in the alt. Do the test like i described in the thread next to yours. 1965-c10. Are you sure the belt is plenty tight.It can slip & cause a low output.

Bill: I was thinking about grounds, and one thing I noticed tonight was that one of the rubber mounting bushings for the regulator was missing. No clue what happened there, but I'll have to take care of it. Now I'm wondering if that is contributing. Other than that, the ground wire is good and tight, no corrosion on it or the sheet metal or where it bolts to the body of the regulator so it does look good.

George: I saw the test you talked about in Woogeroo's thread. I'm going to do that one. As a side note the service manual I have shows a really good illustration of the test you describe. I was going to put my question in Woogeroo's thread but I didn't want to hijack it. I will check the belt too. I did have a little bit of slipping on it on the really cold days we had earlier this week. I just chalked it up to the cold, but I will double check that.

Thanks to both of you. I at least have things to check and rule out first.

The first thing I would do is crank up the idle set screw to eliminate any question of not enough RPM
2. Check voltage going to rotor w/respect to factory spec. IF OK reg is OK.
3. Check brushe(s) on rotor
4. check rotor resistance against fact spec.

Dan Bentler

After doing a few tests it kept telling me the regulator was at fault. I had another on hand and put it on. Yep, fixed it right up. No more ammeter swings, it shows steady charge and the voltmeter agrees. Thanks everyone!