On my 67' impala, the emergency brake light recently started staying on all the time. The emergency brake is pulled up fully and I checked the brake fluid and its good. Also, the brakes feel good so i doubt its them. So, what could be another cause of that light staying on?
When they installed a dual reservoir brake system with a separate brake system for the front and rear brakes; they included a safety switch to inform you of a brake failure if you lost one or the other (since the car would still stop with the working part). That was a plunger that sat in the middle between the two reservoirs with a magnet in it. If the plunger moved it closed a magnetic reed switch lighting up the brake light on the dash.
The plunger will only move if the pressure is greater in one system than in the other (it has a leak allowing the line pressure to escape). The pressure should be the same since it is being pressurized with only the one pedal pushing on the one rod entering the master cylinder. But if your master cylinder is bad, or if you have a bad wheel cylinder, then the fluid can escape and allow the plunger to move.
Check the wheel cylinder cups for leaking brake fluid. If you find any, you have a bad wheel cylinder. If all four wheel cylinders are dry you have a bad master cylinder.
What Dave is talking about is called a differential pressure switch.It is usually in the proportioning valve assembly mounted below the master cylinder on the frame.Has one wire attached.
Or,if it's really the parking brake,check the switch mounted on the parking brake mount under the dash.
The emerg brake light comes on when the emergency brake is depressed only.
There is a plunger type switch attached to the left side bottom of the emerge brake pedal. When you depress the brake pedal it releases the button and the emerg brake light comes on. The cause is most likely a poor adjustment or a broken plunger switch.
1966 Impala SS
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Check the switch first. Mine is also acting and the brake light will come on from time to time. All I have to do then is to pull the brake pedal up and it stops. I think in my case is a weakened spring because there is a play in the pedal when it is released.