Watch for
Fan runs but air is warm
Watch for
Unit trips a breaker or will not start
Watch for
Ice on the coil or water inside
Start with the symptom, not the thermostat alone
“Not cooling” can mean the compressor never starts, the fan is moving very little air, the coil has iced over, the return air is bypassing the filter, or the unit is doing its best with weak shore power. Dometic and Coleman rooftop systems share some patterns but differ in components and controls.
If the unit is icing, running it longer usually does not make it cool faster. Turn it off long enough to let ice melt, keep the return air path clear, and avoid repeatedly cycling power while you wait for service.
Why power quality matters in an RV
An RV air conditioner is a high-draw appliance. A loose connection, undersized extension cord, bad pedestal, or overloaded circuit can create a symptom that looks like an appliance failure. Tell the technician whether other high-draw equipment was running at the same time.