Brake and battery light intermittent

[stlouisaaron]

My 1991 Corolla had a dead battery on Friday night. I replaced the alternator 9 months ago - with a new one. I took the battery in to have it tested, and after charging it was found to be "good". My son was driving it on Friday and said that the brake and battery light started to come on intermittently. Charged the battery and it seems ok - except that the brake / battery lights are still coming on intermittently. Any ideas?

[stlouisaaron]

sorry - I should've started with a forum search. Just got about a million hits on "brake battery light". I'll check the alternator tomorrow.

[RogueMoog]

Yeah, this seems to be a common question / problem. I had this issue several months ago. Since I put a new battery in my wagon (old battery was finished), I haven't gotten the two lights. I would think if the battery was bad, I would only get the battery light coming on, not both, which indicates an alternator problem. Auto parts store free charging system check comes back (three times in the past year) that the alternator is fine.

[Elizle]

If I'm not mistaken, your alternator could be alright but the voltage regulator on the alternator could be bad. I think that was what was wrong with the 91 that I was driving while my fuel pump and distributor were out on my 88. You still have to get the alternator changed though, because the regulator is on the alternator. Not 100% on this either.

[tashirosgt]

Other possibilities:

Check for a broken wire on the 3-wire connector to the alternator. On cars this old, the wires get brittle. If that's your problem, then the alternator may always test good at the auto parts store, but still not charge or only charge intermittently when on the car.

If you water pump starts to go out and interferes with the belt moving, your alternator might stop turning long enough to cause a warning light to come on.