Very odd Power Master Brake operation

[Greg Drenovas]

So this is kinda weird, at least in my experience. So I had a failure today with the power master brake system. Pedal got hard suddenly while driving. So, from this site, I followed the diagnostic information and I believe I have a failure in the pressure switch. The pump will not run at all but the fuse was good. So I checked for brake warning light operation and found that it didn't come on with key on engine off. Therefore, I decided to push the parking brake to see if that light came on then. Not only did the brake warning light come on when I pushed the parking brake, but also, the pump came on with the ignition on. Vehicle running, as long as the parking brake was on and the brake light was illuminated, the pump would work as it should!! I still feel that I have a failure in the pressure switch, but I thought I might post this oddity to see if anyone else has noticed this with a pressure switch failure. Seems that is is not grounding, and maybe can pick up the ground for the parking brake switch when its on??? Also noticed a slight bit of brake fluid in the connector for the pressure switch, so I am leaning toward that as the most likely failure. Please post back if you think Im missing something or am down the wrong road.

 

[PLAINWHITE T]

I had the same issue and also noticed leaking at the pressure switch. I replaced the pressure switch, but then shortly thereafter found that the powermaster motor seemed to have a mind of it's own and run intermittently. That's when I spent $150 to go to vacuum brakes and haven't looked back since.

 

[Greg Drenovas]

$150 wow. What set up did you use? I figured it would be much more expensive than that

 

[BEATAV8]

that is an odd problem for sure

Definitely need a new switch if you seen fluid on it.

I thought the "brake" light is connected to the E-brake switch and the switch on the proportioning valve. Not sure if it's connected to the PM switch somehow. The man to ask is John Spina at Caspers Electronics.

 

[PLAINWHITE T]

$150 wow. What set up did you use? I figured it would be much more expensive than that

If you keep an eye out in the parts for sale section you'll see vacuum conversions from N/A Regals and Monte Carlos in this price range. Do some research on here on Vacuum conversions and you'll find out a lot.

 

[salvageV6]

Check to make sure you have a good ground on Pin C of the powermaster pressure switch after you replace it.

It's the black wire.