I noticed that I have a light in my gauge cluster to notify that the parking brake is set, but it does not work and I cannot find any wires going to the parking brake assembly nor any evidence of where a sensor might have been connected. LMC does not seem to show this on their schematics either. Anyone have any info on where this light is supposed to be triggered from? I would like to get all the electrical items functioning on this rig. Thanks.

 

its not a parking brake light,that light lets one know when one has a problem in the system

 

So is that reading the wires running from the brake line manifold? I wondered what the heck those wires were for. Thanks.

 

The switch on top of the proportioning valve is what triggers this light. From what I've read, if there is a pressure differential between the front and rear brake lines, this switch will activate the dashboard light. I've also read, however, that the switch is a notorious POS that often leaks brake fluid, thus setting off the dash light.

The brake light is on on my dash. I'm going to have another go at bleeding the brakes this weekend with the proportioning valve pin pulled out (again!). If that doesn't remedy the dashboard brake light, I'm going to have a look at the switch.

Fish

 

FWIW mine comes on briefly when I start the truck, possibly only while cranking. If you never see it at all it may be an indicator that something isn't right with the system.

 

Is there any way to "test" this system to see if the light works? I wonder if pulling the sesor would set it off?

 

The light should be illuminated with the key at the "start" position. This is the "test" functionality to let you see if the bulb is good.

The light will also illuminate with the key at "run" if the switch at the brake proportioning valve is closed (i.e. valve is not centered). This indicates a problem with the braking system - often a bad wheel cylinder or brake hose.

 

As a mechanic-in-learning, how does one go about diagnosing a bad wheel cylinder?

Thanks -

Fish

 

Given that I have never seen the light come on, I better start chasing some things down. Thanks for the good info.

 

C8AZ2B264A .. Plastic Low Brake Fluid Warning Light Switch-Threads into Brake Differential Proportioning Valve / Available from Ford and a gazillion autoparts stores.

Fits: 1968/79 F100/350; Econoline & Bronco / All 1968/69 FoMoCo Passenger Cars.

This switch (it's notorious for failing) develops cracks in its threads, causing brake fluid to seep out. When this occurs, the low brake fluid warning light on the dash comes on...and stays on.

 

have any of you guys concocted a way to wire a parking brake switch to the same idiot light? I'm tired of wearing my rear shoes inadvertantly

 

Now this is what I really thought I was fixing, and have had the same challenge remembering to unlock the darn thing. It would be nice.


Thanks numberdummy for the info.

 

I imagine that changing this switch requires bleeding the brakes, correct?

Fish "lots of new guy questions" Scientist

 

The first year of factory installed combination Parking Brake and brake failure warning lamp was 1984 model year.

Numberdummy has stated in the past there is a Dealer add on kit you could get to make the parking brake pedal work the light. I'll let him describe that in detail himself.

 

No, but if you've got a brake fluid leak there, it's because the seals inside the proportioning valve are bad, and you'll need to change it, which would require bleeding the brakes. There shouldn't be any fluid in the cavity the switch screws into.