Brake switch
Thread Starter
Instructor
Joined: Mar 2013
Posts: 180
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From: Chesterfield Mo
Brake switch
With the wire to the brake switch mounted on the frame connected the brake light between the speedo and tach lights all the time. With the wire disconnected the light goes out. What does the light indicate? Brakes seem to operate normally. Master cylinder is full. Do I need a new switch? Car is a 75.
Team Owner
Joined: Jun 2000
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From: Southbound
Cruise-In II Veteran
The brake warning light tells you of a possible problem in the braking system. Time to take a look at the brakes. It is also the tell-tale for the emergency brake. Is the e-brake on while you're doing your testing?
Last edited by Easy Mike; Nov 2, 2014 at 09:12 AM.
Safety Car
Joined: May 2008
Posts: 3,755
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From: Lafayette Louisiana
got the same problem on my 76 now
got the same problem on my 76 now
If I understand your post correctly, yours may be similar.
If your brake light stays on all of the time could be 2 things. One is the emergency brake is on or stuck or your brake proportional valve under the master cylinder is causing the problem. There is a valve and switch in the proportioning valve that detects a difference in brake pressure between the front and back brake systems. If the pressure is different, the warning light comes on indicating a problem.
The easiest check is unplug the wire going to the proportioning valve and if the light goes out, then the proportioning valve is the source. If not, you have got a problem in the emergency brake switch. You can try stomping on the brakes to reseat the proportioning valve switch. That did not work for me. I replaced the proportioning valve.
I suppose the proportioning valve could be working too if you have a brake fluid leak somewhere, but I assume basis your post that you already checked for brake fluid leaks and do not have any.
Hope this helps.
If I understand your post correctly, yours may be similar.
If your brake light stays on all of the time could be 2 things. One is the emergency brake is on or stuck or your brake proportional valve under the master cylinder is causing the problem. There is a valve and switch in the proportioning valve that detects a difference in brake pressure between the front and back brake systems. If the pressure is different, the warning light comes on indicating a problem.
The easiest check is unplug the wire going to the proportioning valve and if the light goes out, then the proportioning valve is the source. If not, you have got a problem in the emergency brake switch. You can try stomping on the brakes to reseat the proportioning valve switch. That did not work for me. I replaced the proportioning valve.
I suppose the proportioning valve could be working too if you have a brake fluid leak somewhere, but I assume basis your post that you already checked for brake fluid leaks and do not have any.
Hope this helps.
Last edited by 20mercury; Nov 2, 2014 at 09:44 AM.
Pro
Joined: Jul 2006
Posts: 505
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From: Buxton Maine
Most likely the valve. It could be stuck from a previous leak. When there's a leak, a plunger in the valve moves to make a connection causing the light to come on. I rebuilt mine rather than replace it since it had the correct date on the valve's body. Got a kit from a place called Muscle Car Research. About $12. Just pressed out the old parts and pressed in the new ones. They get dirty in there from old brake fluid and don't flush out very well so it's not a bad idea to rebuild or replace.
Safety Car
Joined: May 2008
Posts: 3,755
Likes: 721
From: Lafayette Louisiana
good to know, thanks!
Most likely the valve. It could be stuck from a previous leak. When there's a leak, a plunger in the valve moves to make a connection causing the light to come on. I rebuilt mine rather than replace it since it had the correct date on the valve's body. Got a kit from a place called Muscle Car Research. About $12. Just pressed out the old parts and pressed in the new ones. They get dirty in there from old brake fluid and don't flush out very well so it's not a bad idea to rebuild or replace.
(a new proportioning valve costs $100)
