71 F100 Brake Warning Light - Always On

[Chasbod]

My understanding is that the sensor in the brake (proportioning?) valve is what turns the brake light on? What causes this to remain in a steady on position?

No manual at the moment to reference....just you guys.

If this valve block is bad, can you buy replacements?

[1970F250]

if your talking about the warning light in the left side of the dash thats always on. the guy that had my truck before me just took the light out.

[FORDification]

It's a brake warning light, if you lose pressure in the front half or rear half of the hydraulic system it comes on. That thing that looks like an "H" on the frame where the lines go is a pressure differential valve. The valve is centered and balanced by the pressures of the front and rear system. If the front or rear lose pressure, the valve goes off-center and trips the brake warning lamp switch that rides on the valve. It also goes off-center when you bleed the system and can be a real pisser to recenter, especially if you're doing it by yourself. A lot of times people just disconnect the plug to the switch, not the best idea.

Read the following thread on how to re-center it:

http://www.fordification.com/forum/viewtopic.php?t=2214

[Chasbod]

Clear as a bell!! Thanks very much.

Hopefully my manuals will get here soon! I sense a bigger job than expected coming on w/ complete overhaul of brakes that haven't been touched in God knows how long. I doubt the cylinder hone will get used as I will probably be buying new hardware.

[flyboy2610]

This may help with the brakes:
http://www.classictruckshop.com/brake_rebuild.asp

[OLEYELLERTRUCK]

Is that light also for the emergency brake when applied?

[FORDification]

No...but don't worry, that's one of the most commonly-asked questions about our trucks. The light IS located down by the e-brake, but there's absolutely no connection between the two.

[Chasbod]

One other question... Is there supposed to be a return spring anywhere on the parking brake lines and linkage?