1990 charging problem

[drt0800]

Driving today with stereo playing. Stereo started turning on and off on it's own. It's an aftermarket that was in there when i got the car. Battery light came on and my voltmeter in dash dropped to 6 or 7 volts. I checked battery and it tests good. How do i check the alternator? I have a voltmeter. I did attach voltmeter to battery with engine running and it showed 11.70 volts. Thanks in advance for the advice.

 

[KOPBET]

How old is the battery? What method did you use to check it and determine it is ok? Is it at full charge? If not, charge it and check the DC voltage at the battery while running again. Change the voltmeter to read AC volts and check again. If the DC voltage is not around 13-14 volts or the AC volts is more than the millivolt range, you're going to need to have it repaired or replaced.

 

[Hib Halverson]

Driving today with stereo playing. Stereo started turning on and off on it's own. It's an aftermarket that was in there when i got the car. Battery light came on and my voltmeter in dash dropped to 6 or 7 volts. I checked battery and it tests good. How do i check the alternator? I have a voltmeter. I did attach voltmeter to battery with engine running and it showed 11.70 volts. Thanks in advance for the advice.

In addition to "KOPBET's" suggestions, start checking for loose connections near the battery in B+ and grounds.

 

[drt0800]

Charging problem

Just put multimeter on dc volts (20) checked battery with engine off. 14 volts. Started engine, checked with engine running 11.70
put battery on my charger which tests battery. Says battery is good. The charger has an alternator check and that comes up as a problem. I checked ccm and there are no codes
I purchased the car 1 year ago and it's the battery that was in it.

How old is the battery? What method did you use to check it and determine it is ok? Is it at full charge? If not, charge it and check the DC voltage at the battery while running again. Change the voltmeter to read AC volts and check again. If the DC voltage is not around 13-14 volts or the AC volts is more than the millivolt range, you're going to need to have it repaired or replaced.

 

[vetteoz]

with engine running and it showed 11.70 volts.

Battery voltage only

How do i check the alternator?

Good reason to buy a FACTORY SERVICE MANUAL so you have it all at your fingertips

 

[Hib Halverson]

Barring further diagnosis, I'd guess the alternator is bad.

Also, don't trust the meter on your battery charger as with 11.7v with the engine running means the battery is not charging. If the battery is not being charged and that condition has existed for a while, the battery may not be in the condition you think.

Typically, the little meters in battery chargers only read voltage and voltage alone is not indicative of battery health.

 

[drt0800]

Alternator

Turn out it was a bad alternator. Thanks for the help

Barring further diagnosis, I'd guess the alternator is bad.

Also, don't trust the meter on your battery charger as with 11.7v with the engine running means the battery is not charging. If the battery is not being charged and that condition has existed for a while, the battery may not be in the condition you think.

Typically, the little meters in battery chargers only read voltage and voltage alone is not indicative of battery health.