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Old 07-14-2010, 10:50 PM   #1
Dusty71blazer
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Question Why is my Brake light on?

The brake "idiot" light is on, what turns this on? fluid level is fine, brakes work fine, e-brake is released.... what gives?
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Old 07-14-2010, 11:01 PM   #2
Jtrux
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Re: Why is my Brake light on?

Mine would come on when I slammed the brakes and stay on for awhile, no idea why. Just a thought.
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Old 07-14-2010, 11:04 PM   #3
Critter
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Re: Why is my Brake light on?

That light has nothing to do with the Ebrakes in these years. Unfortunatly it only tells if you are having proportioning valve problems. Basically if the front and back system are "out of whack" that light will come on. If the proportioning piston travels too far one way or the other it will activate this switch. Usually it means you have a leak somewhere or a bad caliper/wheel cylinder. It's also possible the switch is just stuck or you have a crossed wire which could be your issue beings the brakes seem to be working fine. See this diagram...there should be a tan wire plugged on to the switch terminal.
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Old 07-14-2010, 11:09 PM   #4
Dusty71blazer
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Re: Why is my Brake light on?

Thanks Critter!
this gives me a place to start troubleshooting....
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Old 07-14-2010, 11:14 PM   #5
Critter
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Re: Why is my Brake light on?

No problem, my Blazer did the same thing (brake system was fine otherwise) I removed the switch and found that it was gummed up and stuck. By the way, the switch isn't in fluid, it is in a dry cavity, or at least mine was, so its easy to unscrew and reinstall.
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72 Chevy CST K5 HIGHLANDER BLAZER Getting a 6.0,NV4500,NP205,14BFF (Currently laying all over the place in little pieces)
72 Chevy swb step-side "LS" 6.0 Here's a build thread of sorts
2002 HD2500 Crew Cab, 8.1L Allison 4x4 Daily Driver

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Old 07-15-2010, 12:22 AM   #6
old man jimmy
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Re: Why is my Brake light on?

critter is right. The end of the switch sets in an indent in the piston, and if it touches the piston it turns on your brake light. But the switch is made of nylon, and if you really crank down on it (too much torque) it will also make contact, and your light will be on, even though their's no problem with the brakes. Make sure your master cyl. is full, and pump your brakes pretty hard a few times, they'll usually go out.
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