john1529

Upon start up ('97LS) when I press the brake to put it in gear the battery light on the dash will flash. This will happen each time of press the brake for a while when I begin driving. The flash is very fast. If I turn the lights on the battery light will stay on for about 2 seconds but afterward the light will not come on again, even when pressing brake. No other problems with lights going dim or car not starting. Battery checked out ok. Any ideas?

Thanks
John

GRAND_LS 4

iTrader: (2)

How long has it been doing this? and how many miles do you have?

This started happening to me in my friends GS a while ago, but it was a little more complicated, and the alternator headed south.

Its either that, or you have a weak ground somewhere.

john1529

Thanks for the reply. I have 100k on it. It started doing it about 2 mo ago. I figured the battery was going because I never drive it but the battery checked out ok. I had problems w/the alternator about 6 mo ago. I changed out the brushes and it worked fine.

alsalih

Yeah I also believe its' your alternator. A failing internal rectifier (diode) will lead to reduced output and will therefore be incapable of recharging the battery at low RPM. That's one risk you run when you replace the brushes on an alternator as the bearings, rectifier, or voltage regulator will eventually fail forcing you to replace it anyway.

john1529

The battery, alternator and system checked out ok.

The battery light flashes when brake is pressed or briefly when lights are turned on. Once lights are on, no more flashing. Seems like the light wont flash when there is more load on the system.

alsalih

A problem with the rectifier will get progressively worse and is intermittent in nature (some times it will only occurs when the alternator is hot), it will not necessarily check out bad if tested on the bench. Mine never tested bad on the bench tester however my problem never resurfaced after replacement of the alternator. The idle speed will increase when you turn the lights on, and also if you turn the A/C on, which is then compensating for the low output during normal idle. Use a voltmeter and check the voltage at the battery with the car running at idle in Park with all accessories off, the voltage measured should be slightly 13.7 to 14.8 Volts, if not then your alternator is not working right.