Had the same prob. it was the Ebrake switch. 
Brake Idiot light
Thread Starter
Instructor
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From: Homer City Pa
Brake Idiot light
My brake Idiot light comes on sometimes for a few seconds sometimes it stays on for a while. My question is what makes it come on? My brakes work fine, fluid is full. I'm not sure where to look.
Le Mans Master
Joined: Mar 2001
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From: Ann Arbor Michigan
Originally Posted by big_G
The parking brake and the brake system failure switch both connect to the brake lamp. 1 of these circuits is on intermittantly. The brake system switch is on the proportioning valve.
Next time it comes on, pull the wire off the proportioning switch, if it doesn't go out then it's the e-brake switch.
Last edited by Duke94; Jul 25, 2005 at 06:10 PM. Reason: typo
Thread Starter
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From: Homer City Pa
Originally Posted by Duke94
I agree if the brakes feel good, gotta be the e-brake switch. Only other possibility I can think of is if the wire to the switch on the proportioning valve is somehow shorted.
Next time it comes on, pull the wire off the proportioning switch, if it doesn't go out then it's the e-brake switch.
Next time it comes on, pull the wire off the proportioning switch, if it doesn't go out then it's the e-brake switch.
Melting Slicks
Joined: May 1999
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From: Moon Township PA
Originally Posted by lil ski
The E Brake has never been used so its probably the proportioning vavle wire I will try that when I get home. The light stayed on all night last night and the brakes felt no different than usal. As always thanks for the help!
Actually, I don't think that the switch on early sharks is anything more than a warning light for low pressure. I don't believe that proportioning valves were used early on. If you can eliminate the parking brake, then you have a bad master cylinder. You will get a flash from the brake light when the MC lets go for a moment or two. I had this situaion on my 72.
Gary
Drifting
Joined: Nov 2001
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From: 68 427 4.11s Roadster
Easiest to hardest.
Cheapest to most expensive.
The parking brake switch is in there with the handle. Don't matter if you ever used it and more likely to be the problem if you haven't.
Think about it, like a door light switch you never use that door but the lights are on. Is the door actually closed? Is the switch adjusted for the closed door?
Or is it the headlight switch? Same concept.
Cheapest to most expensive.
The parking brake switch is in there with the handle. Don't matter if you ever used it and more likely to be the problem if you haven't.
Think about it, like a door light switch you never use that door but the lights are on. Is the door actually closed? Is the switch adjusted for the closed door?
Or is it the headlight switch? Same concept.
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Le Mans Master
Joined: Jul 2005
Posts: 5,752
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From: Austin Texas
Originally Posted by GaryS
What year car?
Actually, I don't think that the switch on early sharks is anything more than a warning light for low pressure. I don't believe that proportioning valves were used early on. If you can eliminate the parking brake, then you have a bad master cylinder. You will get a flash from the brake light when the MC lets go for a moment or two. I had this situaion on my 72.
Gary
Actually, I don't think that the switch on early sharks is anything more than a warning light for low pressure. I don't believe that proportioning valves were used early on. If you can eliminate the parking brake, then you have a bad master cylinder. You will get a flash from the brake light when the MC lets go for a moment or two. I had this situaion on my 72.
Gary
Melting Slicks
Joined: May 1999
Posts: 2,897
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From: Moon Township PA
Originally Posted by big_G
The proportioning valves were first used in '67 vettes. The switch IS a bias-failure device. It lets you know that one of your brake systems (front or rear) has a problem......
Gary
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From: Homer City Pa
I removed the wire from the proportioning valve and the light went off. But that didnt solve the problem. The light would not stay on all the time but the brakes did seem to be working fine. I took the car out on a back road ran it up to about 55mph and spiked the brakes hard. The light went out and has not come back on since maybe the proportioning valve was sticking a little and that freeded it up. What ever it did it worked so far. Thanks for all the help. 
Melting Slicks
Joined: Nov 2001
Posts: 2,668
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From: Eastern US XX
Originally Posted by big_G
The proportioning valves were first used in '67 vettes.
Proportioning valves didn't arrive until the 70's - I believe somewhere around 75.
Last edited by pws69; Aug 10, 2005 at 08:17 AM.
Le Mans Master
Joined: Jul 2005
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From: Austin Texas
Originally Posted by pws69
Incorrect. It just monitors pressure differential between front and rear and if one leaks, the piston will go to that side and turn on the light.
Proportioning valves didn't arrive until the 70's - I believe somewhere around 75.
Proportioning valves didn't arrive until the 70's - I believe somewhere around 75.
Well, I'll call them that, due to the restrictor in the block for the rear brakes....I have had all year "Proportioning" valves apart, up to the '82's. I never saw any type of "Valve"...lol, just a piston with o-rings...looks like a spool valve....
Le Mans Master
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From: Austin Texas
Did you disconnect the "Proprtioning valve" switch connector? If so, then pull the parking brake housing, disconnet the p/b switch and see if the light goes off. If the brake light goes off when you disconnect the p/b switch, repair or replace it.
Le Mans Master
Joined: Jul 2005
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From: Austin Texas
Early C-3's they are mounted on the master cylinder with a bracket, the others are mounted either just below the alternator, on the frame, or on the frame at the bend just below the drivers door front edge...G/L
Le Mans Master
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From: I can walk to MA
Originally Posted by neilb33
what about a 1980? That box next to the alternator to the left?
proportioning valve or distribution block - whatever you want to call it.
I bet it's on the frame rail - down near the drivers floorboard, but follow
the lines - they will go right to it.
