Brake bleeding/proportioning valve reset

[87r10owner]

I have an 87 R10 that I swapped the rear-end out and it and the brake light on the dash stayed on! I did bleed them after and found that a wheel cylinder was leaking so I completely rebuilt all my brakes with all new parts. Once again I bled the brakes and it still stays on so the proportioning valve I'm guessing is stuck to one side. So how do I reset it and get that light off??? What it the rubber button on the side of it for?
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[Desert1957]

Originally Posted by 87r10owner

I have an 87 R10 that I swapped the rear-end out and it and the brake light on the dash stayed on! I did bleed them after and found that a wheel cylinder was leaking so I completely rebuilt all my brakes with all new parts. Once again I bled the brakes and it still stays on so the proportioning valve I'm guessing is stuck to one side. So how do I reset it and get that light off??? What it the rubber button on the side of it for?
Posted via Mobile Device

That button re centers the spool in the proportioning valve, you can also bleed the front brakes to recenter the valve.

It senses any loss of pressure and seals off the opposite side of the brake system so you can still have some brake pedal in case of a fluid loss situation.

Here is a BASIC pic of how the valve works.



Note these brake systems are getting old and that valve can stick.


Desert

[jjzepplin]

Mine was stuck (or so I thought) for a long time. I finally took it out and looked down the switch hole after removing it and it didn't look to be out of whack. Then I got in there and worked the piston back and forth and it was hard at first but got easier. Then put it all back together and the light was still on. Seems someone had it apart at some time and forgot a washer under the switch as it was down too far and the switch was always tripped. Might have jammed the piston and kept it from moving at all. works great now!