Brake and Battery light on?!

alaniscool

Senior member
Jul 30, 2000
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Hi,

My car's brake and battery lights are on (sometimes alternates between on/off while I'm driving), even when I'm driving (definitely with my handbrakes off). Is this indicative of something serious, or just my lights going crazy?

Thanks
 

Thegonagle

Diamond Member
Jun 8, 2000
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Probably your alternator. The reason your brake light also comes on is probably because many cars have the brake lamp "test" tied into the alternator light, which is fine when everything is working normally, but confusing when it's not. Ignore the brake light if it is never on with the alternator light off, and get the charging system checked while the light is on.
 

Tominator

Diamond Member
Oct 9, 1999
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Originally posted by: Garfang
Probably your alternator. The reason your brake light also comes on is probably because many cars have the brake lamp "test" tied into the alternator light, which is fine when everything is working normally, but confusing when it's not. Ignore the brake light if it is never on with the alternator light off, and get the charging system checked while the light is on.

Assuming the belts are tight, the problem would be evident even if the light were off. Most alternators have a diode bridge and if one diode were to burn out the voltage would drop. The alternator would still put out some charge and possibly the voltage drop is just low enough to trigger the warning light.

Take it to an Auto Zone, Pep Boys or any large chain. They will test your chargeing system for FREE.
 

Lvis

Golden Member
Oct 10, 1999
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Years ago my toyota did that when the voltage regulator was going bad. Rather confusing have two lights come on at once. I though there might be a short in the dash lights or something.... then the battery died.
 

alaniscool

Senior member
Jul 30, 2000
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Well I took my toyota to two different autozones and they said the battery and alternator was fine. Is the voltage regulator part of the alternator?
 

alaniscool

Senior member
Jul 30, 2000
254
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yep, it's a little bit under the max line. There's plenty in there before it gets to the min line.
 

Tominator

Diamond Member
Oct 9, 1999
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Originally posted by: alaniscool
Well I took my toyota to two different autozones and they said the battery and alternator was fine. Is the voltage regulator part of the alternator?


I mosr cars of today the regulator is in the alternator. Even if it wasn't, the test would have included it. If it was bad the test would tell you.

How often does the light come on? Has it been doing this for sometime?
 

alaniscool

Senior member
Jul 30, 2000
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well, it's been doing it for at least two-three weeks now, and it comes on and off whenever I'm driving...however I noticed that when I'm driving on the freeway, then both lights tend to go off.
 

Tominator

Diamond Member
Oct 9, 1999
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The faster an alternator turns the more current but it would have shown bad in the test irregardless.

Could be just a lose wire some where. I'd keep a close eye on it until there are other problems that might be associated with this.

I would not trust the car for a long trip and be prepared for a tow. Carry some jumper cables with you.

...And a flashlight!