break warning light on - why?

[ibbis]

On my 89 Silverado the break warning light wan't go off anymore. Why?

The break systems seems not to have a leak (aplying pressure to the pedal gradually and steadily - pedal does not sinkto the floor)

The fluid level in the master cylinder is fine.

The parking break switch is operating normal (if I apply the parking break the break warning light will light a little bit brighter).

 

Besides the master cylinder is a switch. To the upper side of switch is a 12 Volt cable conected.

I think this is the switch for the 2 break systems. How to check this switch?

On one side wall of this switch is a contact (covered with a little plastic cap). Its also with 12 Volts

 

An ideas???

[1998Z71]

I have a 90 1/2 ton 4x4 Chevy that had a similar problem. Not sure if the 89's had rear anti-lock brakes, but, the module for the rear anti-lock brakes gave out on mine. I just unplugged it and the light went out. If the light goes out, the module is bad. I've been driving it like that for several years now without any problems.