HMMWV Brake Warning Light

[dskupi01]

I am working through the diagnostics via the TMs and the wiring diagram on a brake warning light (on after parking brake released). I could use some help understanding the function of the pressure sensor on the proportioning valve.

Precursor,
I had a Cadillac valve hose leak. Leaking/dripping the day prior. I likely got oil and subsequently water on the proportioning valve. I don't believe i leaked enough to put air into the power steering pump/hoses.


Brake warning light is still dimly lit after parking brake is released. Brakes work fine (not driving it until diagnosed). I have good brake pressure and function. Good accumulator. All four wheels seam to be grabbing equally.

Working through the wiring diagram, removing the plug to the "brake warning valve" switch on the proportioning valve makes the light go out.

Does anyone know how this valve/sensor works? Is it default shorted, and goes to open circuit with startup? If yes, what conditions? Does it go to close circuit if front and rear pressure on brakes not even (lower pressure on one)? Think contamination could ruin this switch? Any suggestions on next steps to diagnose, vs throwing parts at it?

The front and rear chambers on master cylinder are both full of Dot 5 fluid. Bled brakes about 6 months ago, with no problems.

 

[dskupi01]

Light was dim (not fully lit). Removed connection to proportioning valve brake pressure sensor. Cleaned out water and transmission fluid from the sensor. As mentioned, I had a leak from Callilac valve hose, and used water to clean up the mess. Sensor was saturated with oil and water. After this, reconnected all, and the dim light diminished to nothing. I think a small amount of stray current was going to ground through the sensor, and causing it to dimly light

 

[DREDnot]

I would give both sides of the connector some attention with compressed air. Then scrub everything with a q-tip and alcohol. Finish with a dab of dielectric grease around the contacts to ward off moisture and corrosion.

 

[porkysplace]

This is a generic diagram of how the proportioning valve works and the switch . You may need to take the switch out and center the pressure rod .