Topic: Emergency brake switch/light
in Forum: C3 Electrical
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My emergency brake red light on the dash is on all the time. I have removed the switch from under the console and cleaned. No matter what I do with the switch the light remains on. I can even disconnect the one wire that goes to the switch and the light still remains on. I have looked at the Corvette wiring diagram and there is only one wire 18-tan/white going to it from a terminal strip. Where else could the problem be?
Thanks
Mike
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The Brake light is not only for the parking brake...it is also used to signal a problem in the main braking system. The switch for that is on the proportioning valve, located on the frame down under the brake booster area. Just follow the brake lines down from the master cylinder, and you'll see a brass block with the brake lines going into it. You'll also see a wire hopefully connected to a switch on that brass block.
Do your regular brakes work well?
Do your regular brakes work well?
Joel Adams
C3VR Lifetime Member #56
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Hi Mike, The brake light can also be on due to the "low brake" switch being activated. This switch is meant to indicate a low brake fluid condition or excess travel of the pedal. If that switch is shorted or stuck, the light will be on. I hope that this helps!

Joe T
Thanks for the help. My brakes work fine and my fluid is ok with no signs of leakage. I found the wire that goes to the switch on the valve. How do you get the wire off? Can the wire be removed to isolate the problem to the valve?
mike
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The wire connector should just pull off. If you dis-connect the switch/wire, and the Brake light goes out, there is a problem either in the brakes themselves(which you say work fine), or the switch is bad. If you disconnect the wire and the light stays on still, then it's time to trace that wire circuit for a short.

Joel Adams
C3VR Lifetime Member #56
My Link
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Joel,
Thanks for the help. It turns out that the switch is bad. The brake lines to the valve are very rusty and I am concerned that it I attepmt to replace the valve I will have a major project. If I watch the master cylinder level, leaks on the garage floor and operation of the brakes what is the down side for leaving the switch dissconnected?
Mike
States I visited
Hi Mike, It is possible that there is a "hidden" problem with the braking system and not a faulty switch. The "78 owner's manual points out that driving with the light staying on could be a safety issue, so you may want to have the brakes checked out. I don't recommend leaving the switch disconnected. Joe

Joe T

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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
I kinda agree with Joe on this...
There's really no way of knowing if the switch is bad, or if there is a problem with the brake system.
The purpose of the switch is to warn the driver of a failure in the brake system. If you lose pressure in the system, either to the front OR rear brakes, the p-valve will flip to the end that works, and at the same time, it will ground the switch, which causes the light to come on. Sometimes, simply bleeding the brakes can cause the p-valve to flip. Either way, the switch has been grounded for some reason or another.
If your brake pedal is firm, is not going down too far, and the cars stops very well, then it is entirely possible the switch just got stuck in the grounded position...but...the only way for that to happen would be for it to have been grounded to begin with.
For instance, at one point, the brake system had a failure, the p-valve flipped, and grounded the switch. Then, the brakes were fixed, but the switch just got stuck. IN this case, changing the switch itself would prolly take care of the issue. The switch is replaceable(in most cases) without having to replace the p-valve. The switch simply screws into the p-valve. You'll lose a bit of brake fluid changing the switch, and the brakes will need to be bled afterward.
You can certainly leave the wire to the switch hanging, and it will not cause any problems with the brake system. However....I would make dang sure the brakes were indeed working properly if I did that.
There's really no way of knowing if the switch is bad, or if there is a problem with the brake system.
The purpose of the switch is to warn the driver of a failure in the brake system. If you lose pressure in the system, either to the front OR rear brakes, the p-valve will flip to the end that works, and at the same time, it will ground the switch, which causes the light to come on. Sometimes, simply bleeding the brakes can cause the p-valve to flip. Either way, the switch has been grounded for some reason or another.
If your brake pedal is firm, is not going down too far, and the cars stops very well, then it is entirely possible the switch just got stuck in the grounded position...but...the only way for that to happen would be for it to have been grounded to begin with.
For instance, at one point, the brake system had a failure, the p-valve flipped, and grounded the switch. Then, the brakes were fixed, but the switch just got stuck. IN this case, changing the switch itself would prolly take care of the issue. The switch is replaceable(in most cases) without having to replace the p-valve. The switch simply screws into the p-valve. You'll lose a bit of brake fluid changing the switch, and the brakes will need to be bled afterward.
You can certainly leave the wire to the switch hanging, and it will not cause any problems with the brake system. However....I would make dang sure the brakes were indeed working properly if I did that.

Joel Adams
C3VR Lifetime Member #56
My Link
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
in Forum: C3 Electrical
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