Any ideas why RV rooftop A/C short cycles?

[reader2580]

I have a RV rooftop A/C that is short cycling. The compressor runs for about 45 seconds and shuts down. A few minutes later the cycle repeats again. The air is cool, but not cold when the compressor runs. Any ideas?

I suspect it lost the refrigerant, and is going out on low pressure. It isn’t typically economical to repair one of these if it lost refrigerant.

 

[gmcgeo]

Low refrigerant most likely, I'd be guessing though without being able to test.

 

[reader2580]

RV air conditioners are typically a sealed system with no Schrader valves to check pressures. It is possible to add them, but not always cost effective To do so.

 

[fitter30]

Could be short of refrigerant like other wrote. Running for 45 second system needs more time running to start producing cold air. System holds very little refrigerate losing two or three ounces could make it short. It's a sealed system trying to find a leak would almost be impossible to find and the labor would be cost inhibitive. Take the outside cover off coil could be dirty, fan motor for the condenser might of be running see if the fan blade turns easily and with power off look at the wiring.

 

[reader2580]

The blower is running. Most of the time the same motor is also running the condenser fan.

I have not been able to pull the cover off yet to if I can see any issues.

 

[reader2580]

Of course, now another of my three A/C units has failed. The fan on the other is spinning at half speed. I had pulled it apart this summer to clean it. At the same time, I pulled out the capacitor and tested it. It was barely below the specifications on the label.

 

[reader2580]

The blower on the one unit went back to normal speed after turning it off for a bit. This morning it started not starting without spinning the motor by hand.

I am going to have the motor rebuilt as no direct replacement motors exist.

 

[Codyboy]

Weird. You sure the power to the RV is good?

Low voltage, missing a leg and back feeding through a 240 appliance?

 

[reader2580]

Running on generator the whole time. Generator is 120 volt. I checked voltage and it was 120.x volts.

 

[reader2580]

All three of my rooftop A/C units had issues at one point, or another, on my trip. The final one failed twelve miles from home while making the last fuel stop. It is at least giving a code that generally indicates either a dirty condensor coil, or a bad capacitor. I have not had a chance since getting back late Tuesday to look at any of the air conditioners.

I am very much leaning towards one, or more, mini splits instead. I worry about the copper lines breaking in a mobile application, but I have talked with people who have mini splits in enclosed trailers, and leaks. An enclosed trailer is going to be even worse than a motorhome for bouncing around. I would also consider the new PEX style refrigeration lines. They are not cheap as I probably need to buy a 300 foot roll of each size for my application, but copper is not cheap either. (I can apparently get custom lengths from the manufactuer.)