1980 Brat charging issues

[Tweek]

Hey Y'all, outta the blue, the brake and chg light started coming on at idle. If I leave it idling, it will suddenly die. Initially, I could rev it up and it would go out and stay out, staying running until the key was turned off. Repeat that and drive, no probs. Now, it won't stay off after the rev trick, coming back on as soon as it returns to idle. I also need higher revs while driving to keep it off. Load tested the batt and replaced. New battery didn't cure. Alternator I assume? Are the internal voltage regulators adjustable to kick the alt on sooner? Or is it just worn out and ready for replacement. How's the napa rebuild for $40?

[naru]

Internal voltage regulators are not adjustable.

Your 80 should have an external reg.

The original ones are adjustable,but,you do not want to go there.

 

Alternator probably just needs brushes.

$40 is pretty cheap,but,if you are on a tight budget,just replace the brushes.

[mikaleda]

IMHO That sounds more like a voltage regulator than the alternator. Take you alt to napa they can bench test it for free that will tell you if it is your alternator or not, good luck!

Edited February 6, 2013 by mikaleda

[maestro]

If you have a voltmeter set it to DC. Place the red probe to the positive on th battery and the black probe to the negative while the engine is idling. Idle should be 800-900 RPM's and you should be seeing about 14 volts at your voltmeter and not fluctuating. If you see less than 14 your alternator is not putting out proper charge and needs to be replaced. With the probes still attached to the battery rev the engine to say 2500 or so RPM's and watch the needle. If it starts to flucuate you probably have a bad regulator. If the needle goes up and doesn't fluctuate then as others said the brushes are probably worn and need replacing. As far as whether  to replace brushes of the whole alternator I suggest replace the whole alternator. If you can get a whole one for $40 that's not too bad, probably comes with a warrany and is a much quicker replacement to swap out alternators than replacing brushes.

 

Another alternator test, that I do not endorse as it has been said it can damage the charging circuit on a car, is to remove th positive cable from the positive post on the battery while it is running. If the car dies you have a bad alternator. If it continues to run then you have a good alternator. Like I say do this at your own risk and depending on how brave you feel. They say is can cause damage to the car. I have done it many times and nothing has happened to me but maybe I am just lucky.