Brake Light

[Scott91370]

Out of the blue the brake light came on. Plenty of fluid, parking brake switch not sticking. Truck stops great.
If I unplug the wire on the proportioning valve the light goes off. Do this 'go bad'?

 

[Ricko1966]

You can pull and test the switch. If the switch tests good,it's almost certain that the shuttle valve is not centered. That would mean you dont have enough pressure on one circuit of the brakes and a thorough brake inspection is needed.

 

[Sad Sack]

What he said ^^^^^
Plug this into CoPilot and you'll get some ideas: On my 1985 GMC C1500, the brake light is on. If I unplug the wire on the proportioning valve the brake light goes off.

 

[Scott91370]

Thanks guys!

 

[gofone]

If it has ABS disconnect the ABS module , they had trouble with some of them

 

[Scott91370]

If it has ABS disconnect the ABS module , they had trouble with some of them

No ABS on an 85.

 

[Ricko1966]

I don't think they had true ABS on any square. They had RWAL but it was mechanically controlled

 

[Keith Seymore]

Make sure the park brake isn't on (or the pedal drooped down).

K