Expert: Kevin Pilotte - 3/16/2004

Question
Hello.
This is my second attempt. I somehow wiped out the whole question a minute ago.?
I am working on a 74, AMC Javelin, 304,Auto,AC,
Power Disk Brakes,.
I am working towards passing State Safety Inspection and use as a weekend driver.
While working on the Brakes I noticed two things.
One- the wire on the Proportioning Valve was not connected.
Two- the Dash Brake warning light does not come ON like the Alt and Oil light when attempting to start the engine.
When I touch the wire to ground with the ignition key on the light does come on. It does not come on any other time before or since I have hooked the wire back on the PV.
( Note: I have replaced - calipers, wheel cyl, pads, rear drums, all spring hardware, bled the lines,turned the rotors, bearings,,,etc.)
My questions are.
1. When working properly does the ignition switch put a ground on the Brake light wire to test the lamp when starting. I guess this indicates there is an open in that area.
2. How do you test that the PV would put the needed ground on that wire when brake line pressure is lost. For that matter how can you confirm the PV is working at all. Am I right that it's main job is to regulate pressure and prevent rear wheel lock up.?
Test rides around the block with fast stops from up to 40 MPH all worked fine.
Thank You For Your Time,
Dave
PS. Are multiple / on going question OK?


Answer
1) When the key is on, the brake light should illuminate for a bulb test, HOWEVER, if the sensor wire is disconnected, it ain't going to happen.
2) The Combination valve does a few things. It senses a loss in pressure in either the front or rear hydraulic system. It activates the dash light if it does. It also is suppose to maintain the correct pressures, front to rear, to provide balanced braking.  What has happened is someone bled the brakes without properly holding the metering valve portion. Try removing the switch where the wire goes to, pump the brakes a few times, then reinstall the switch and wire. This is suppose to center the valve inside. If it doesn't, no biggie. It shouldn't effect the braking of the vehicle.