Brake Light & Battery Light on

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  #1  
Old 06-05-07, 06:51 PM
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Join Date: Apr 2005
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Brake Light & Battery Light on

Hi,

I own a 1990 GMC Sierra 1500 with 177,000 klms on an 8 cylinder 305 and just today my 'battery' light came on and the in-dash voltmeter shows approx 10V. Seeing this I thought damn my alternator just died and it's not charging and I'm running off my battery which is going to die soon. So I drove home, left the truck running and popped the hood. I put a voltmeter across both battery terminals and got a reading of 14.4V! What could be the problem?? Defective in-dash voltmeter?? Bad ground somewhere?? Bad battery?? The battery terminals are not loose.

Also my brake light came on a couple days ago. I needed front brakes (which I thought caused the light to come on), so I replaced them today, topped up the brake fluid and the brake light is still on. Any ideas what could cause the brake light to remain on?? I replaced the rear brakes last year. I did not see any leaks today (wheel cylinders, calipers, lines, etc...). Could it be the master cylinder?? The brake pedal is right up and does not go to the floor.

Thanks for any info!
 
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  #2  
Old 06-05-07, 07:37 PM
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Join Date: May 2007
Posts: 115
Well, you've definitely lost a connection between your alternator and the vehicle system.

Its not unheard of to have battery cables corrode within the cable between connections; I've had a vehicle suddenly not start and the cable was corroded at midpoint - no breaks in the plastic covering, either. Your job now is to hunt down the bad wire(s).

Brake light will come on with low fluid - but you topped that up. Is your parking brake slightly on or the switch out of whack?
 
  #3  
Old 06-06-07, 04:31 PM
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Hi,

Thanks for replying back! I'm not sure what you mean by "between your alternator and the vehicle system."? The alternator is charging 14.4 volts when I put a meter at both battery terminal posts. But the gauge in the truck is showing 10 volts and the battery light is on.

I did pull on the parking brake release to ensure it wasn't on and while I pulled the release, I also lifted the parking brake pedal, but the light did not go out. I will check the switch for the parking brake tho.

Thanks!
 
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