Quote:
Originally Posted by 1976gmc20
4x4, yes. I think special-K or someone on here said these trucks had RWAL.
Either one, I would just like to delete (probably isn't working anyway). I drove for decades without either one of those 
Sorry to interfere in your build thread. |
I'm pretty sure that's right that they only got rear wheel. it's probably not too hard to delete, just look at the wiring diagrams and see what components ground the light.
as far as "interfering", it was on topic discussion, and we are all here to learn from one another, I have no issue with anyone posting here, as long as it's on topic.
Quote:
Originally Posted by 68Timber
I've read something here about the PV reset getting tripped, it happened to someone else here once.
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There is so much miss-information out there on the combination valve, the PV doesn't have any components to "trip". I did a quick write up on the components, and what they do.
on the left, you have the front brake outlets, if desired, theoretically, you could plug one of the front outlets and run a "T" off of the other to supply both brakes, it really doesn't matter which goes left or right. there is also a metering valve, which allows the rear brakes to apply slightly before the fronts(this is important in later discussion).
in the middle section, you have both inlets from the master cylinder, a warning switch, and the shuttle valve(switch piston).
on the right, you have the single rear brake outlet, and the porportioning valve. many people refer to the combination valve as a porportioning valve, but it is only part of the assembly. the porportioning valve prevents rear brake lockup on a panic stop by limiting flow to the rear, and creating a more gradual apply.
the center of the shuttle valve has a detent which operates the warning switch. in the event of a brake line failure, pressure on the side with a failure will drop, and the side without failure will be much higher, which in turn results in the valve moving to block the port of the failed section. when the valve moves, the detent activates the switch triggering a brake warning on the dash.
now, for front failure, there is a button on the side with the front brakes, which allows the valve to be reset and the brakes bled. but there is not a reset for the rear, that's because the metering valve should allow the valve to reset itself. in the case of a rear system failure, there are a few options to fix it, the more difficult and painful way, is to disconnect the rear brake line from the porportioning valve, remove the porportioning valve (
***it's reverse thread!!!***)and use a pin to reset the valve. reassemble the components, and then let the rear circuit gravity bleed. there is a tool that can be installed in place of the brake warning switch to keep the shuttle valve from actuating, this will allow you to go straight to a normal bleeding procedure. the second option is more debated than the first, but should work when performed properly. with the light on on the dash, now stomp on the brake pedal, but almost as soon as your foot hits the pedal, get off of it. the metering valve will allow rear line pressure to build sharply, but not the front which should cause the valve to shift towards the front circuit and reset.
mine tripped last night while I was trying to bleed the brakes, and I decided to sleep on it. woke up this morning, did some reading, went out to reset it, and the light was out... so time might also help reset the valve, although, I wouldn't bank on it, I may have just been lucky.