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Old 05-26-2010, 05:01 AM   #1
91ma70
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Default Dimming headlights and interior lights?

Okay one more thing, i have a problem where the headlights and guage illumination will dim significantly when i hold the brake. the volt meter dipps to around 11-12v when this happens, normally its around 14v. I suspect that its the alternator or could it be the battery or something else? temporarily i rev to 2k rpm @ idle sometimes and let the lights comeback to full strenght. Any Advice?
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Old 05-26-2010, 07:24 PM   #2
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sounds like the alternator. go to autozone and have them test it.. it's free. report back once thats done. if the A.Z person gave your alternator the all clear we can go over some more possibility's.
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Old 05-27-2010, 03:59 AM   #3
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yeah, thats what i was going to do. hopefully thats the problem since i have a new alt sitting in my garage somewhere.
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Old 05-28-2010, 01:49 PM   #4
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dude i had the same problem except i had a new alternator...i thought i had a short circuit since the battery would end up dead sometimes...it ended up being the pulley...i had to put a tiny pulley because according to gear ratio, the smaller the pulley the more revolutions its makes with one spin of the crankshaft...that pulley cured the problem
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Old 05-28-2010, 07:01 PM   #5
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Changing the pulley could make it work for awhile, but that's nothing more than a band-aid. Spinning the alternator faster to compensate for an improperly working part will just put more stress on other parts of it, such as the bearings, causing it to fail early.

bryanf89, I suspect your new alternator was defective from the start (every manufacture has a certain percentage of defective parts).

I would suggest that both of you take your alternators (with the factory pulleys) to an auto parts store near you and get them tested. Also check the wiring coming from your alternator to make sure it's not old and brittle, as this can cause poor charging. If you have a voltmeter, you can check the voltage at the positive lug on the alternator and a chassis ground. With the engine running, you should have around 13.5 volts. Now check the voltage at the battery (still with the engine running). If the voltage deviates at all, you need to inspect/replace your wiring.

Let us know what you find
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Old 07-06-2010, 07:10 AM   #6
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So i change the alternator, seems to work fine now!
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Old 07-06-2010, 04:42 PM   #7
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glad that worked out!
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Old 07-10-2010, 06:14 AM   #8
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haha the same thing happened a few days ago! turnout to be the battery this time. Anyway replaced it and so far so good..
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Old 12-31-2010, 02:37 AM   #9
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I had a problem with my alternator. Went to Schucks and had it tested. failed both times. so i bought a new one, but the headlights still dim when i press on the brake. the new alternator puts out about 13v. my battery is about a year and a half old. just checked up on it. put some more water in the holes. my alternator belt pully is a little squeeky. I dont know whats wrong with it. i know almost nothing about cars. I've had my dad and my boyfriend both look at it but they've never worked on a supra before so they dont know what to do either.
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Old 12-31-2010, 07:11 PM   #10
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Quote:
Originally Posted by Homicidal Hippie View Post
I've had my dad and my boyfriend both look at it
glad to see in this day and age people aren't afraid to show who they are..

so new alternator? good battery? your belts are a tad squeaky, best replace those.
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