Charging system

[dragway]

I have posted a this question before but didn't get clear answer. Tested charging system on my 87 gn with light on it charges at 12.9 Checked that with my buddy's 87 gn and the same is that normal seems a little low to me.

 

[novaderrik]

was that the voltage at the battery with the car running?
if so, sounds about right for most cars, but my car is 13.5 or so at idle.. my Nova was 13.8 at the battery after swapping in a CS120 alternator..

 

[dragway]

That is at the battery

 

[Hotrodbuick]

12.9 seems a little low but not too bad. Were the fans on and lights also? What is reading with everything off at battery and on back on alternator? Mine shows at battery about 13.7 or so with everything off.

 

[turbo nasty]

Typically its upper 13's..check cable connections...clean and secure. You may also want to check the volt light in the dash for corrosion on the bulb connections thats a common issue.

Posted from the TurboBuick.Com mobile app

 

[salvageV6]

If the battery is fully charged it would be a normal voltage.

To do a quick check leave the lights on for 15 minutes car OFF, read the battery voltage, then start it and see what readings you get charging.

 

[earlbrown]

The battery might just be old and sulfated and 12.9 is all it can hold.

 

[Ttype6]

with light on it charges at 12.9

What light?

 

[turbodave231]

Guys, 12.9 volts at the battery with the car running is WAY TOO LOW! With the healthy battery that is 75% or better SOC, the voltage should be 14.2-14.6 volts. If the battery is low or junk, the battery maybe pulling system voltage low.

 

[dragway]

Battery is new connections are clean just add a new ground strap still same 12.9 at battery and back of alternator

 

[salvageV6]

What was the charging voltage after leaving the headlights on for 15 minutes with the engine off?

 

[Hotrodbuick]

Check connections at back of alternator, if everything looks good there pull alternator off and take it to local parts store, they can test it for you. That will eliminate that part of the problem if its good or bad.