Powermaster unit gurus

[S2V6RACER]

Well, I've never had a problem with a power master untill today.

Here's the scoop. The unit looks to have been replaced sometime recentley, but the accumulator is the old one. The switch is the grey one. This is what it does.

The motor kicks on like it should (when the key is first turned on), but as it is building pressure, in about 5 seconds, the motor begins to slow down(normal), but never shuts off. The RPM's go real low but it just never kicks off. The pedal is fine and if I pump the brakes there is a good pedal and the motor speed increases untill I stop pumping the brakes.

My concern is the motor gets EXTREMELEY hot and I know i'm going to burn it up if I run it. I am leaning toward the switch BUT I have access to a used old style accumulator right now. I am just looking for some opinions, maybe somebodys been through this before.

Of course I'm going to Norwalk so I have 1 day to iron this thing out, figures.

Thanks. Ted

 

[ChrisCairns]

I would also lean towards the pressure switch but........

Straight from the GNTTYPE webpage:

__________________________________

Step #4 - Motor does not shut off with ignition on

A. Check fluid level per Step 2A.
B. Install J35126 tool per Step 2C and test to determine if fault is in motor and pump assembly, pressure switch, or internal booster leakage.
C. Monitor booster pressure on J35126 gauge - After 20 seconds with ignition on and without braking.
1. If pressure exceeds 770 psi, replace pressure switch.
2. If pressure does not reach 540-770 psi pump shut-off range, check the front and rear holes in the bottom of the reservoir on boost side only.
a. If fluid is flowing into the reservoir through either hole, the booster is leaking internally and the complete powermaster assembly should be replaced.
b. If fluid is not flowing into the reservoir through either hole, the pump is unable to provide 540-770 psi and the motor/pump assembly should be replaced.

 

[Brian Harper]

I would definitely say the pressure switch. That poor little pump is working its brains out and the pressure switch isn't shutting down the pump when the pressure is good. Check out this link :
http://www.gnttype.org/techarea/brakes/PwrMstr.html

and for a diagram on the powermaster wiring, check out :

http://www.gnttype.org/techarea/images/PwrMstr.gif

I had the same problem, only different - my pump wouldn't start. It turned out to be a bad connection on the pressure switch, but I'll bet your pressure switch is bad. Try the troubleshooting guide in the first link.

 

[S2V6RACER]

Thanks guys. I looked over the Gnttype.org site last night.

The pump is definatley working it's butt off.

I am leaving at about 12:30 to fix the car and heading down to Norwalk.

Ted

 

[DAILYFLOGGER]

Yup

Strikes me as a switch problem. Does the motor stop if you disconnect the 3 wire plug to the switch?

Another more unlikely cause would be the relay contacts not releasing.

Hope youv'e already got this worked out.