That usually indicates that the Powermaster's accumulator ball may be going. However, if the pedal feels good, and your machine stops properly, you're probably OK for a while...but I'd start looking for a deal now on a new one.
Do you have a line lock ???
I have one and the break light has been coming on / off ever since. Many attempts to solve this have prooved futile. I have a new power master and believe I am getting a false positive that sends the light off.
no line lock or any other work ever done to the brakes,,,could the light be coming on because I need new brake shoes,,,,guess I'd better check them this weekend thank
More than likely Quickwrench got it right, as my Brake light problems sound just like yours. Brake light came on/went off for around 2 years before it went completely bad, since installing the accumulator ball, all the problems have gone away!
Yes, the parking brake and brake system share the same warning light.
I've had good luck with my A-1 Cardone reman PM. Lifetime replacement warranty. I was able to keep the pressure switch and accumulator for spares when I turned in the core.
Check the accumulator, if you have the the stock one. I woud definately day it is the problem. Last summer, I had the same problem. Replace the acc. and no problems since. $140 or so for the part.