The stock gage in my 87 NA has indicated 12 volts when in gear since I’ve owned the car. However, the gage read closer to 10 volts at idle. I also notice a slight dimming of the dash gages and headlights at idle. Should I be concerned? Any suggestions for fixing this?

 

Have the alternator tested. Sounds like you lost a rectifier.

 

Aaron, Thanks. I replaced the alt about a year ago. I also had the new one tested a week or so ago and it was fine. I agree that it sounds like the alt, but it doesn't appear to be.

 

Bad alt... check the diodes/rectifiers in it. Easy to do... set your meter for AC voltage and test between the charging post and the body of the alt. If you have any AC voltage the alt is failing and has lost at least one or two of the diodes/rectifiers in it.

BTW, any time the voltage is less than 13.5 volts, you are not charging the battery, and less than 12.6 volts, you are running on battery power...so since you have been driving like that for a while, chances are the needle on your volt meter is bad

 

I've replaced the alt but am still having the issue. I've also had my new alt bench tested and it reads 14+ volts and idle and under load. The battery cables have also been replaced.

What else could it be? Do I just need more amps? Am I missing wire or ground?

 

SVS, I think that Icemark's last paragraph was suggesting that it is the voltmeter in your gauge cluster that's going bad. He pointed out that you've been driving the car with low voltage for a while now which if it was true that you really only had 12 volts your car wouldnt be running. So since you are running, then something is lying to you (the gauge)

 

go out and get a cheap voltmeter gauge

 

I agree that the gauge is not reading correctly. However, the drop at idle is quite noticeable. I'm mostly concerned about it. I don't want the car turning off on me after sitting in stop and go traffic for a while.

 

check the Battery Voltage..with the cables disconnected..then Check it again with engine ON..The altenator should put out approx.13.8 volts..the battery Should be getting that,engine On..If the battery cables Reads Lower,then I would Try another Battery(since you said your alternator is new)..My S4 would Read 12.and dim sometimes on the Lights.at idle..and change a bit when revved.I changed the alternator to a FD alternator(puts out around 100 amps..)It fixed the problem.I knew my Battery was good though,because it is a Optima,and was Fairly new..

 

I have a voltage problem as well. i changed alts and still no luck

when i idle low and go from a stop my car will sometimes die on me because im not gettting enough voltage to the tps etc.

I boosted my idle up to 1500 and got a better battery and my car runs a bit better. thats the quick fix. I am still trying to diagnose my problem

have you tested the wire that excites your alt with a test light?

 

My car has an issue --- when the engine is cold and I start it up it will read 14.1 - 14.3 volts on my commander.

After the car is fully warmed and engine bay is hot, the voltage drops to 13.4 - 13.3