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yourpcgeek49 · 06-04-2016, 07:27 PM

We have a Dometic 59516 rooftop A/C on our 5th wheel trailer. We are currently in Sedona, AZ, but the temp has been hitting 100+. Our A/C will run about 4 hours in the morning and then it will throw the circuit breaker. The compressor in the rooftop unit is way too hot to touch. I have replaced the circuit breaker (it was tripping at 13.5 Amps on a 15 amp circuit.) After letting everything cool off for a couple hours (still in 100 degree afternoon heat) I put a clamp on amp meter on the feed wire and turned on the A/C. It started at 12.5 Amp and gradually increased to over 17.5 amps, then the breaker popped.

Is my compressor shot? I would expect that the A/C "should" be able to handle 100 degree temps, even if it had to cycle on & off for thermal protection. Anyone got any great ideas?

BFlinn181 · 06-04-2016, 09:22 PM

If the condenser and evaporator coils are clean, your filter is clean, next you can test the start/run capacitor. It might be failing and allows the A/C to start when 'cold' but when hot it can't overcome the resistance of the hot system.
There are many videos on Youtube about testing or changing the capacitor, here's one:

https://www.youtube.com/watch?v=Z0X5l8Q7auE

If the capacitor tests out within specs, I'd agree, the compressor is shot. Unfortunately that means a whole new A/C, the compressor and coils can't replaced separately.

MtnTrek · 06-05-2016, 11:22 PM

Looking at the specs on that unit, I'm curious?

Mod.59516, 15K BTU, compressor = 12.9 amps & Fan motor 2.9 amps. = 15.8 A. @115 V. Either device could be over amp. both may have run capacitors.
Although four hours is a fare amount of time to run with a defective part...

"AC circuit protection (user supplied) 20 amp ACAR circuit breaker or time delayed fuse."?

You checked your amperage, what was your voltage? Campground infrastructure (pedestals, etc.) can have loose connections. Shore power cords and connecters can overheat and cause resistance also. Voltage droop could be happening also. Low voltage = increased amperage.

Like BFlinn181 suggested, be sure the condenser coil is absolutely clean of dust and debris. The fan which is equipped to run at 3 speeds should be running at high speed in that environment and temp. The blade should be tidy also. Excessive head pressure = increased amperage.

When it is running in the night or early morning in that four hr. period the suction line back to the compressor should be cool to the touch.

Units are rated for 100+ but efficiency decreases as well as discharge air temp inside will rise.
If the compressor is bucking the breaker or the thermal overload frequently, with no apparent cause it's days could be numbered.

Sorry you're having troubles.

adamfolger · 06-06-2016, 12:29 AM

Simple things first. Is the power cord too hot to hold just before the plug. Make sure the blades of your power cord are not glazed up (brown looking). Clean with emery cloth. I some times get a 25 degree drop in plug temp after cleaning, when customers, at our park complain of breakers tripping. Not always so simple but often solves the issue.