2007 Cobalt - brake lights being weird

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Old 03-31-10, 06:09 PM
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2007 Cobalt - brake lights being weird

In the morning, I am headed to look at this car for a friend. I am told the center (third) brake light works, and the turn signals work, but the lower brake lights do not light up. Hard to accurately diagnose when I haven't even seen the car yet, but given what I have been, do anybody have any advice? I am told the fuses have been checked and are good, and the brake light bulbs have been replaced. All red lenses in the back; same bulbs for brake and turn? Brake light switch output go through turn signal switch like my '60's GM cars? Thanks in advance - Chris
 
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Old 03-31-10, 08:19 PM
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the way to go is look at auto zone parts finder to see what type of brake light bulb it uses, if it is a dual filament bulb then yes the same bulb is both turn signal and brake light, if it is a single filament bulb then it is separate bulbs for turn and brake, if dual filament the problem is probably in the turn signal switch, or a bad ground at the bulb socket, my money is on the turn signal switch if it has that system. other wise check the brake light switch or even the cruise control cut out switch most likely that brake light signal runs thru it.

Murphy was an optimist
 
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Old 04-03-10, 04:08 AM
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Hate intermittent electrical issues with a passion! When I got to the car, the brake lights were working fine. The socket for the left one was kind of hanging half out of the reflector, but functioned fine. Perhaps the problem was a trick of the setting sunlight. Time will tell. Thanks anyway! Chris
 
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Old 04-03-10, 07:35 AM
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Be *darn* sure the bulbs are factory specification bulbs and they are installed correctly.

You may be able to go to a wrecking yard, find the same vehicle, and see what bulbs are in that and how they are installed.

Don't assume the fuses are good. Check them! How to test fuses...
Testing fuses Page

Your owner's manual should show locations of fuses. There can be several different locations. And several different fuses relating to brakes.

Also if there is trailer wiring installed, check that.

If all else fails, a factory service manual set of books would have detailed troubleshooting instructions for this (and every other problem). Order that from helminc.com
 
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