Powder Coating Parts

DGC

Senior Member
Trying to track down an annoying gremlin. Floated this in General Tech, but believe this may be electrical.

Brake warning light comes on after ~30 minutes of driving. No brake fluid leaks at wheel or MC. No fluid loss from MC chambers. Brake proportional cable pressure differential switch is properly connected to aftermarket proportioning valve. Relevant details include willwood d52’s on the front and s-10 upgraded rear wheel cylinders. OE electrical MC has been replaced with a Strange hydraulic unit (with appropriate brake pedal and firewall mount bracket). Brakes work fine. Hard stops can be made without rears locking (proportioning valve working fine??).

Additional details:

1. the bulb test of brake warning lamp on ignition does not illuminate the light

2. depressing the e-brake increases lamp illumination by a large amount when compared to the dim warning while driving. e-brake switch does not appear to be the issue.

3. using Classic Performance Brake Proportioning Valve PV-2. problem occurs with the pressure differential switch connected or unconnected.

Checked shop manual and Powermaster connector short of leads B and C of this connector would be source of low brake fluid psi. Since Powermaster has been replaced (Strange), the three-prong Powermaster connector is unplugged. Shorting leads B and C of this connector does not illuminate warning light???

All this raises the question of where a low psi signal is coming from?? I can drive the car with gentle acceleration without the warning light illuminating. Modest acceleration triggers something that powers this light. Light will remain on from that point. Restarting from a cold engine finds the brake light to be off. Once the light has illuminated, however, restarting a warm engine does not reset the light, it stays on. Throttle body vacuum block has new silicon lines (passenger side) and vacuum to Powermaster capped off. Brake cleaner squirt at TB does not affect rpms.

Odd type of gremlin. but for peace of mind, I need to track this down. If anyone can point to the shop manual location of wiring, I might
be able to identify a cross-over current from another source?? any suggestions would be appreciated.

DGC
 

Chuck Leeper

Toxic old bastard
Staff member
" OE electrical MC has been replaced with a Strange hydraulic unit (with appropriate brake pedal and firewall mount bracket). Brakes work fine. "
So, the powermaster is removed?
"Brake warning light comes on after ~30 minutes of driving. "
Could be, the system is getting residual pressure, due to heating the fluid.
An easy test is to drive the 30 mins, then crack a bleeder, and see if there's pressure built up.
If this is the case, the mc rod is holding the mc piston in far enough, to disallow fluid return.
 

6Packer

New Member
"problem occurs with the pressure differential switch connected or unconnected"

that's a head scratcher!!!!.....the e-brake & pressure differential are two different switches / same light aren't they??
debris in fluid ??
 
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