brake warning light (reset?)

[1971ford]

i know there is topics on this light allready and i dont know if this should go in a different section but my brake warning light stays on all the time. My dad and I thought it was that the front brakes werent working but today we found out that they most likely are working (he bleeded the brakes). so i dont know why that light is coming on. the brakes seem to be fine. is there a way to "reset" that light?

[cghstrojan08]

I had the same problem. All my brakes were fine but the stupid light would be on. So, I just took the bulb out and not more light.

Some way you are supposed to get equal pressure on both sides of the brake proportioning valve (that is where the sensor is). I tried and tried with mine and said the hell with it.

[fordman]

yes you have to recenter the valve on the distribution block under the cab inside the frame rail follow the purple wires down the front of the firewall.

[AustinTom]

If the brakes were all bled then I think it should reset itself. At least mine did. That little light is a very handy thing to have when you got a leaky master cylinder.

[HOWDY69]

I had to bleed mine several times to get the valve to move back to center. I think you bleed the side opposite the side that had the brake problem. The valve moves over to block the bad side so you need to bleed the good side. If it will not center there is something wrong with a brake line or wheel cylinder or the valve is just plain stuck. When mine finally moved I heard a pop.

[FORDification]

Here's what the drum-brake distribution block looks like:



...and here's what the manual says as an example of how the valve works:

Should a failure of the rear brake system occur, hydraulic fluid pressure in the rear brake system would drop. During brake pedal operation, the fluid pressure buildup of the front brake system would force the differential valve toward the low pressure area (secondary system outlet port). Movement of the differential valve forces the switch plunger upward over the taper shoulder to close the switch electrical contacts and lights the warning lamp, signaling a brake system failure.

...and here's how it describes the proper procedure for centering the valve:

Turn the ignition switch to the ACC or ON position. Loosen the pressure differential valve inlet tube nut of the unfailed system, or the side opposite the system that was bled last. Operate the brake pedal carefully and gradually until the pressure differential valve is returned to a centralized position and the brake warning light goes out. Tighten the tube nut.

Basically, it's just telling you to crack either the front or rear brake line while a helper pushes on the brakes very slowly until the light goes out. It'll probably take a time or two to get it just right. It's really kind of a PIA to get centered...more annoying than difficult.

Hope this helps....good luck!

[fordman]

cool

[heep70]

Do what Keith said. it is pretty easy to do. Might take a few tries. If you push to hard or to fast then the ball will slip to far and end up on the other side. At that point you have to tighten the side you are on and losen the other side. You will here the ball click as it moves. If you think you have it make sure to re-bleed the system and give it a test.

[ezernut9mm]

so, how does a person know which is the "unfailed" side? do i just throw a grenade at it to see if it explodes? looks like this might take a while.

[fordman]

trail and error. or maybe the low side of the master cylinder might give a hint if its low that is.

[FORDification]

You just need to move that valve one direction and then the other and watch the light. I'd just crack a rear inlet tube nut while someone in the cab pushes on the brake pedal and watch the light as the pedal goes to the floor. This will either:

A) cause the valve to go off-center more (if the valve is already pushed to the rear), so nothing will happen...or
B) bring the valve back towards the rear from the front (if the valve was pushed to the front)

If it doesn't go out, then crack a front inlet tube nut and watch the light. At some point it's going to go out. The hard part is closing the bleeder as soon as it does go out.

[Supermike]

I'd just crack a rear inlet tube nut while someone in the cab pushes on the brake pedal and watch the light as the pedal goes to the floor. ... If it doesn't go out, then crack a front inlet tube nut and watch the light. At some point it's going to go out. The hard part is closing the bleeder as soon as it does go out.

Umm... call me stupid, but where do I find the "rear inlet tube nuts" and/or the "front inlet tube nuts"?

I think I'd better hire a professional.

[fordman]

its the ones coming from the master cylinder.

[FORDification]

The rear reservoir is for the front brakes, the front reservoir is for the rear brakes. Just follow the lines from the MC down to the distribution block...and where they hook up is where you'll loosen them.

[Supermike]

Thanks... any suggestions on which side to try first? LOL! I guess I could technically bleed all the fluid out before I get it right myself...