SC Charging Problem Feedback

DonM#47 · 08-17-2013, 08:27 PM

My '82 SC has a charging problem. Battery is new and shows 12.8v. After starting, meter shows 12.6v - a little too low, right? Switching on the headlights brings the meter reading down to 12.1. I've got a small battery for weight and the car won't run far with that reading. Revving to 2500 RPMs brings the meter to 13.8v - not bad, right? Still, when driving at night, the battery will eventually lose too much power and will eventually not produce more than a 1000 RPMs.

I know the battery is small, but there's no A/C running or other drain beside the small radio. If the alternator could get 13.5+ to the battery, size wouldn't matter, right?

It seems that there is something in a wire or connector that is preventing the engine idle level charging to get up to and above 13.5v.

Any other thoughts on what else to consider.

S2GART · S2GART's Garage

12.5-12.8 is fine when the engine is not running. However, once the engine is running, the reading should be 14-14.3. It should stay at this reading no matter what RPM or what accessories are on.

You say the battery is small. What size battery do you have in the car. The size of the battery only comes into play for starting the car. Meaning that it has enough CCAs for the engine. Once the car is running, what is really running the engine is the alternator via the battery. If the battery isn't being continually and properly charged, then the battery has to make up for the lack of voltage from the alternator. This of course leads to be stranded on the side of the road......

Pull the alternator out and take a look at the VR's brushes. Also examine the slip rings on the alternator. It sounds like your alternator is the culprit.

DonM#47 · 08-17-2013, 09:22 PM

Quote:

Originally Posted by S2GART

Pull the alternator out and take a look at the VR's brushes. Also examine the slip rings on the alternator. It sounds like your alternator is the culprit.

Thanks. I've been afraid that the alternator had reached its "time". I was hoping someone might send me in another direction. I guess it's time to get real with the alternator.

S2GART · S2GART's Garage

Have you ever pulled the alternator out before? When you do get it out, take it to a local shop that rebuilds alternators and have them take a look at it. It may be a simple fix/repair. They should be able to test the alternator, independent of the VR. This would tell you if you are in need of a rebuild.

I had an issue for the longest time of the "fasten seatbelt" light coming on when I accelerated and then my tach needle would bounce all over the place. I pulled the alternator and had it tested. Though I was fairly certain it was the VR. The shop told me that typically what goes on alternators is the diodes. Saying that when these alternators get old, the solder connections fail. My alternator which is original (car built in 1982), was in great shape and they confirmed my suspicion that my problem was the VR.

DonM#47 · 08-18-2013, 12:38 PM

Quote:

Originally Posted by S2GART

Have you ever pulled the alternator out before?.

Thanks, again. Alternator removal looks a bit time consuming but not difficult. It does sound like I've just a got a weak one. The voltage builds with the RPMs, but never quit gets to where you would expect it. Across the RPM range, it seems to be about 1v short of what I need.