reason for break warning light?

[SebringYves]

On my '89 Silverado the break warning light is always on. Why this? The break switch for parking break seems to be okay. The Mastercylinder seems to be fine also. I couldnt find any leak and the fluid level is fine.

What can I do?

[North Coast Hotrod]

My 89 K2500 has the same problem... Haven't been able to figure it out either.

Paul

Originally Posted by SebringYves

On my '89 Silverado the break warning light is always on. Why this? The break switch for parking break seems to be okay. The Mastercylinder seems to be fine also. I couldnt find any leak and the fluid level is fine.

What can I do?

[nitowl]

JUST A THOUGHT......
My 90 does the same thing. BUT ONLY STARTED when my brake light
switch got messed up. Had to readjust my brake light switch so
brake lights worked again but dash light never went out again. Maybe I actually need a NEW brake light sw. Hate to buy one if I dont actually need one. Or maybe it has nothing to do with it...coincidence?
Maybe, Maybe not ........I HATE ELECTRICAL !!!!

[Kevcules]

Brake light on here too.

Does your brake light on dash get brighter when you press on emergency brake? If so, it is probably your rear anti-lock system acting up.(RWAL) I believe most newer trucks have this , my 91 does. Your brakes will work fine except your rear will never anti-lock. So what! Check with mechanic on pricing a fix if you want to.
It may be your centering valve in the brake master cylinder. This will get off center if your system has had a leak or just wear ,and you have less resistance one side of cylinder forcing the valve to move and that will trigger a trouble light.This "might" be centered again by pressing hard on the brake pedal before starting the engine. Then unplug neg battery for ten seconds and see if trouble light is out.Otherwise check for a replacement master cylinder assembly.

Good luck