As is always the case last Friday while it was 110 degrees here in Bakersfield CA our rear AC/Heat Pump tripped the breaker. When I reset the breaker the AC came on but in Heat Pump mode even though the Comfort Control was in Cool mode. Got a tech to come out but by the time he got there it was again putting out cool air. He tested amp draw but could find nothing wrong, of course an hour after he left the breaker tripped again and it was again in heat mode when I reset the breaker.
Since it was the weekend I decided to try to troubleshoot the problem myself. After reading up on this type of problem I thought there was a problem with the solenoid for the reversing valve. I checked the voltage going to the solenoid and found it was 56 volts instead of 110 volts. I tore apart both front and rear units and compared the ohm reading of the rear solenoid with the front one. Found it to be the same so when looking elsewhere for the problem. I found some burn marks around the starting capacitor so I took it out and found it to be burned from one of the terminals to the metal case of the AC unit.
On Monday I started calling RV parts places most needed to order the Start Capacitor but one place had it at 39.95. I then called an electric motor repair shop and they had the exact replacement for 9.95. Needless to say I picked it up and replaced the failed one. Everything is now working correctly. Cool Air at last.
Morale to the story, the compressor may still start with a starting capacitor that is shorting to ground. However since the reversing valve solenoid is connected at the capacitor if there is a short there may be too much of a voltage drop to get the reversing valve to work. You learn something new every day.
Second point if the part you need is used in non RV applications it may be available much cheaper it you avoid RV suppliers.
Dave & Jeri
06 Holiday Rambler Endeavor
TOAD 15 Lincoln MKX