I noticed that my A/C compressor cycles on and off at times, even when the desired temperature has not been reached. I did not notice it until I was running the fan on low speed one time. I have the fan set to "Auto" so it shuts off when the unit shuts off. I also notice that the A/C unit starts, runs for several minutes, then the compressor comes on rather than it starting right away. I intend to query the dealer on this to see if this is abnormal. This is my first Dometic A/C unit so maybe this is normal. Has anyone else experienced this? This a Dometic 15,000 BTU unit and is new (purchased in May).

Rick there is a "Freeze sensor" on most of the newer A\C units. What is happening is that it is seeing a "Freeze condition" on the condensor. It will shut the compressor down until it senses that the condition is no longer. It then starts the compressor again.

You mentioned you fist saw/heard it when the fan was in the low setting. That further confirms my suspicion. The lower air flow is not allowing enough transfer from the coils to the air. Thus it freezes.


The fan starting before the compressor is another built in timer function to also help prevent the freeze condition.

This is the reason I usually leave the fan on high. I do not use the auto setting. With the high humidity we have down here they tend to freeze up quite easy.

Thanks Don, so you feel this is normal? The unit seems to be cooling OK. We have not had a problem with the trailer being too warm, even on a 99 degree day.

The air conditioner will work better on high and with the fan running continuously. I use automatic when the trailer is in the yard and I have the air on and with no one in it.

It's just that the fan noise bugs my wife so it's nice when it turns off.

We run our A/C units with the fans in the "on" position as the change in ambient noise level when the fans cycle on and off is more disturbing to us than the constant dim "white noise" of the fans running continuously.

Running the fans on the "low" setting will obviously reduce airflow across the evaporator, making the evaporator more prone to icing up. The freeze sensor on the face of the evaporator coil will, thus, cycle the compressor more frequently when the fan is on the "low" setting.

Rusty