My brake lights began coming on automatically

Tiny
BRADWRIGHT
  • MEMBER
  • 2001 PONTIAC SUNFIRE
  • 130,000 MILES
My brake lights began coming on automatically. It seemed to drain battery so I replaced brake light switch and battery. It ran one day but battery appeared drained again next morning. I replaced ignition switch and checked altertnator. It ran a couple days but wont even turn over now. I tried to reset the anti theft by leaving key on for 3 ten minute intervals but not having any luck. Any ideas?
Saturday, November 17th, 2012 AT 4:05 PM

7 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Are the brake lites still coming on? How did you check your charging system? Did you check for excess battery drain, before you replaced anything? Does the battery have a full charge, now? If you have a digital multimeter, we can help you do some testing.
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Saturday, November 17th, 2012 AT 4:14 PM
Tiny
BRADWRIGHT
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  • 4 POSTS
The brake lights aren't coming on anymore. I checked the alt and battery by removing and having it tested. I dont have the multimeter.
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Saturday, November 17th, 2012 AT 4:26 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
You need to have the charging system tested on the vehicle. If there is problem with wiring circuits, testing the alternator off the vehicle, won't test the wiring circuits to or from the alternator. A low end digital multimeter doesn't cost much. It's better than nothing. If your going to work on your own vehicles then you need a few diagnostic tools.
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Saturday, November 17th, 2012 AT 5:40 PM
Tiny
BRADWRIGHT
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  • 4 POSTS
Thanks for the advice JDL. I'll locate a multimeter and get back to you.
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Saturday, November 17th, 2012 AT 6:00 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hey man, let us know what you find.

If you place the meter leads across the battery posts, everything off, the generic spec for a full charge is around 12.6 volts. Take the same reading with engine running. The second reading should be higher than the first, if the charging system is working.

You an leave the leads hooked up during cranking, If the reading drops much below 9 volts, you need to get battery charged. Also, make sure battery connections are all clean and tight on both ends.

Yes, on some year--makes and models, if the battery voltage is lost, the vehicle can go into theft lock.
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Saturday, November 17th, 2012 AT 6:43 PM
Tiny
BRADWRIGHT
  • MEMBER
  • 4 POSTS
Problem solved. I started a charge on the battery and noticed sparks when I hooked up. I went back to the brake light switch and adjusted it. There was a piece of loose electrical tape off the pedal. It fired right up. Thanks, you saved my sanity.
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Saturday, November 17th, 2012 AT 7:20 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hey, glad you found it, good job.
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Saturday, November 17th, 2012 AT 7:43 PM

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