Ok so i got a brake light that radomly came on today after i left the gas station. So i did some first checks to see if the light would go out. Filled the master clyinder with brake fluid, made sure the e brake was all the way down, check under the car by each tire to see if it was dripping out when pumping the pedal no fluid poured out on the ground. What could be the problem im having. 88 gta with 89 pbr rear end if this helps an stock single cast iron calipers up front stock 88 master cylinder an proportional valve.

 

70 views an nobody knows what could cause this i just tryed bleeding all calipers an the light is still on someone please leed me in a direction

 

Manual:

"The valve and switch are so designed that the switch will latch in the "warning" position once a failure has occurred. The only way the light can be turned off is to repair the failure and apply a pedal force to develop approximately 450 psi line pressure."

JamesC

 

When mine was coming on and going off [ coming on randomly ] it was the master cylinder.

 

Mine came on with wheel cylinders then again with the brake booster.
check the simple things first. Vacuum hose come off? That little valve the vacuum hose connects to broken /not functioning?
Proportioning valve ok?
Air in the master cylinder? Yes you can bleed the brakes and still somehow have to bleed the master cylinder.
Is the car making enough vacuum to support the brake booster?
There are so many variables.

 

Maybe check the switch at the base of the handle?