Brake Light on Dash wont go off

[69Early]

I had a brake fluid leak in the line from the master cyl at the coupling to the proportioning valve and lost mucho brake fluid. Repaired the leak, filled the master (both reservoirs) blead the brakes and they seem to work fine. However, the light on the dash below the ignition switch is still on and wont go off? Any ideas on what to look for as a problem. Dont want to loose my brakes if there is something wrong or is it a light error problem. Is there a reset or something I dont know about ??? Something to do with power steering? All suggestions would be greatly appreciated!

 

[bert]

Some vehicles had a pressure differential valve that turns on the light. One side has front brake pressure and the other side rear brake pressure. It will have a one or two terminal electrical connector on it. When there is loss of pressure in one circuit the light will come on. Most are supposed to reset automatically but don't always. If the leak was on the front bleed the rear carefully while watching for the light to go off and visa versa for the rear. You are attempting to center the switch again. Good Luck bert

 

[Jeepster]

After repaires have been made and system bled.......To centralize the valve turn the ign sw to on or acc. Slowly press the brake pedal down and the piston will center itself, causing the light to go out.

 

[tcjones76]

You need to "reset" the proportioning valve:

Make sure master cylinder resevoirs are topped off.

1. Turn the ignition switch to the ACC or On position.

2. Push the brake pedal down, and the light should go off.

3. Turn the ignition switch to the OFF position.

That's the procedure from the '76 Ford Truck Shop manual, good luck.

 

[TexasBronco]

Mine use to work properly, then I installed a centech harness, and now mine stays on permantly. I will try the post above mine and see if that works....otherwise I am just cutting the power wire to the light.

 

[Jazona]

My 69 had rust in the porportioning valve so when I lost pressure to whichever, front or back, I had to really stand on the brake pedal to get it to center. Eventually traded the stock valve for an adjustable and lost the light.

 

[Broncobowsher]

The early pressure differential switches are not self centering. That was added later to keep technicians from just unplugging the wire after they fixed the problem because it is such a pain to get the light off correctly.

Turn the key on, make sure light is on.
have a second person open a bleeder on the side you did NOT work on.
Slowly press the pedal until the light goes out. What you are trying to do is reverse the pressure imbalnce and get the valve centered again.
Then close the bleeder as soon as the light goes out.
Then release the pedal.

That should do it. There is a good chance that the gunk in the brake lines may jam the valve in place. In that case unplug the wire.

 

[bnk70bronco]

I just unplugged the wire. what is the light telling me that I don't already know when the pedal goes to floor. Is the light there to tell me to brace for impact?

 

[69Early]

No Luck, Made sure the MC was topped. Slowly pressed the brake (hard) several times and all I could see was the light dim a little for a split second and that was it. I checked the proportioning valve and it looks pretty new. It's brass about an 1 inch wide and 3 inches long. Two inlets on one side (at each end) from the MC and two outlets on the other (at each end)and an electrical plug in the center. At one end there looks like an adjustment nob or cap not sure what it is though. Had power steering and front disc installed about 6 months ago so not sure if it was replaced then but it is definately not original. Also they put and adjustable valve (Wildwood) on the rear to back off the pressure on the drums a bit to work better with the front disc?? Would that be the problem? I want to thank you guys so much for your insights. Although just a newbie, eventually I can hopefully help someone else out on this site. What a wealth on knowledge!! Any more ideas??

 

[Krusher]

Had the same problem with mine after my rebuild. New master cylinder, hard line, wheel cylinders, shoes, drums, the whole enchalata. Finally took the distribution block out and disassembled it. The piston was stuck at one end from age and moisture attacking the inside of the brass block. I used a .22 caliber brass bore brush and an electric drill to clean up the inside of the distribution block so the piston could travel freely, and polished up the piston with some emery cloth. Problem gone.