1995-2004 P32 Chassis J71 Parking Brake Pump Cycles On and Off Very Rapidly.
When the pump cycles rapidly, the poppet valve is not seating in the pressure switch bushing cavity.This is allowing the pressure to drop from the fluid escaping back to the reservoir. The escaping fluid is dropping the pressure, and closing the pressure switch. When the switch closes, it is momentarily activating the pump motor to rebuild pressure. Once the pressure is built this opens the switch, and repeats this process very quickly over and over.
When this is happening it could be the valve or valve seat having an issue, but is usually caused by the spring either not being reinstalled properly or not at all when the bushing is removed or replaced. This can also be caused by a weak spring. We recommend replacing the poppet valve and spring together.
Replacing your poppet valve and spring.
- Place your coach into park and turn off your ignition switch.
- Remove the pressure switch in the side of you pump assembly.
- Remove the bushing that the switch was installed in.
- When removing the bushing you will find a small spring behind it.
- Remove the spring.
- Use a pencil shaped magnet and insert it into the bushing cavity in the pump. Pull back on the magnet and it will bring the poppet valve out with it.
- Inspect the spring and valve for damage, as well as seat for the poppet valve in the pump housing.
- Install the new valve into the pump housing using just your finger.
- Install the spring into recess in the back of bushing using some wheel bearing grease to hold the spring in place as you install it into the pump housing.
- Reinstall the pressure switch and test pump operation.
If you need to find a wiring schematic for your coach, you can find them listed here https://www.ultrarvproducts.com/Workhorse-Manuals
You can find the discussion about this parking brake system here: https://help.brazelsrv.com/hc/en-us/community/topics/360001057571-J71-Parking-Brake-System