95 Monaco Pacbrake problem

[csp]

We have a 95 Monaco with a 300 cummins. When applying the pac brake, it sometimes works and sometimes doesn't. Sometimes it kicks off and on. Does anyone have an idea of what we need to check?
Thank you,
Chris

[deandec]

Some rigs are set up so that the Pak Brake will not engage if the Cruise Control is active. (Mine works regardless of the Cruise Control activation.)

My Pak Brake will not engage if the speedometer reads higher than 65 MPH even though the exhaust switch is on and the throttle is not engaged.

My Pak Brake will only engage if I release the throttle and the PB switch is in the on position.

If you have other examples of conditions where the Pak Brake does not engage perhaps you could describe them so that others might comment.

[jimkate]

Checking Pac Brake operation is frustrating because the activation circuit is tied into the transmission circuits, and nothing happens until the coach is in gear and rolling down the road at a certain speed.

However, I found a way to set up a test circuit to see if the actual exhaust Pac Brake is functioning properly. From the Pac Brake that's mounted just below the exhaust manifold, trace the air hose from it back to the electric solenoid that feeds it. Find a place to obtain live power and feed that power through a switch to that solenoid. Then, with engine running at high idle, you can activate your switch which will in turn activate the solenoid which will in turn activate the Pac Brake. Wonderful.

You can lubricate the Pac Brake to make sure it is not sticking. There's a correct lubricant for that.

Beyond that, it's difficult. My Pac Brake will stick in the On Position and shut us down on the highway in the middle of traffic. So we have stopped using the Pac Brake all together.

[RVhauler]

Pac brakes seem to have a history of sticking if not constantly used. for that reason i went with US Gear for my brake. It activates it's self twice every time the engine is started to test operation

[wheato22]

The Pacbrake is activated by compressed air via a solenoid that in turn gets +12 volts from a series of relay contacts. A bad contact in one of those relays would cause intermittent Pac operation. I diagnosed a similar Pac failure on my coach by tracing the 12 volt signal to the solenoid... looking for the point the 12v signal get lost. I used an inexpensive 12v battery powered test light I found at Harbor Freight and 35 feet of cheap speaker wire with alligator clips fastened on both ends. This way I could watch the test light sitting in my lap while the test leads were connected to the solenoid input wire 30 feet away... all while driving and operating the Pac on/off foot switch.

I found the links for PacBrake wiring diagrams using the following link:
Cat c7 engine brake, Jake Brakes, exhaust systems - Installation procedures and Schematics

From here I selected Medium Duty/Cummins/Engine Brake and went to the end of list where wiring schematics are listed. I selected: http://www.pacbrake.com/PDF/L5430.PDF as it was the closest to my engine type, transmission and on-board air compressor and foot push button configuration.

My problem was a intermittent ground connection at the solenoid.

Larry

[wrangler05]

I drove a 96 Dynasty for 100,000 miles and had no trouble with Pacbrake. However, early on I went to a seminar on it and was told that three locations on Pacbrake need to be lubricated with a NON petrolium based lubricant. One I had was made by Loctite.

[csp]

I wanted to thank everyone for the responses. I lubricated the brake and found the selenoid to be lose where it bolted on. One of the two or both fixed the problem. It came in handy coming down the rocky mountains.
Thanks again Chris