Several weeks ago I posted that my aux compressor would not start if the head was pressurized. I'm pretty sure that was a bad diagnosis. The non-starting symptoms are repeatable with zero PSI.
Once the pressure switch is calling for air, if I give it a firm bump or slap anywhere on the body of the motor or the compressor it starts. I know next to nothing about electric motors. I do know this unit has brushes and that they are a maintenance item. Also suspect that a prior long-standing air leak caused this compressor to run a lot.
Ideas?
Starting the compressor by hitting it could be caused by a sticking pressure switch. Test this by using temporary wires directly from the battery posts to the compressor motor (by pass the pressure switch). My auxiliary compressor did not work when I purchased my U320 because the pressure switch orifice was plugged.
That's a great idea. Will try this.
Actually you can tap pretty hard on the pressure switch cover and if the compressor starts... you found the problem. The U shaped metal can be removed in order to clean the contacts or push down on the actual mechanism. No danger of a shock because it is all 12 volts. Cleaning the contacts may be necessary - try paper strips drawn through the cantacts as you hold them together by slight downward ressure. Pull paper strips through several times. Black on the strip indicates removal of debris. Good luck,
Jim
Finally got time to troubleshoot this issue and the pressure switch and solenoid are working fine. The aux compressor has +12vdc and a solid ground on the power lugs (tight and clean). A moderate thump on the casing of the aux comp motor gets it going every time.
Mike
Might be time to look at the brushes.
Sure sounds like worn or stuck brushes.
Yup, could be worn brushes, flat worn out compressor, or just big voltage drop to a degree that starting is difficult.
I would pull you toad up close (battery side) to it and use jumper cables to the compressor. The large gauge cables should give minimal voltage drop. If pump now starts as it should, start looking at connections, both positive and ground and perhaps up-size wiring (up-sizing ground wire to chassis metal would be very easy.
I have never heard my aux pump run, but coach stays level when parked for weeks/months at a time. I suppose my question to the group would be how would I test the pump? Create a leak by loosening an air bag line?
Thanks
Mike
Disregard...found it on beamalarm
Pulled the aux compressor out of the coach and removed the end plate to access the brushes. Cleaned out a ton of residue, appears to be graphite / carbon powder. Bearing felt good. One of the two brushes was sticky, didn't slide back and forth like the other one. Took some electronic cleaner spray and washed it out. Moved freely after that. Tomorrow I'll get it hooked up and see if this solves the intermittent starting.