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Dometic AC Will Only Run On High Fan Speed

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Hello Everyone! For about the last two years the AC in our 2014 Puma travel trailer will only operate on high fan speed. As long as we start the fan on high then switch over to cool the AC run perfect and cools the camper as it should. If we switch it to low or auto, we can hear a click in the control board (above the filter inside the camper) but the fan will shut off. If we try to start it on low or auto, we get the same click and no start. If we wait a few seconds, we can hear the compressor humming but no fan. I have tried switching out the thermostat but that didn't help. I'm wondering where to go from here... Control board, fan motor, or something else?? Any help would be great!

Rene T:
Welcome to the forum. Just a little tip. You only need to post your question in one section. If the forum staff feels that your post would get better coverage or exposure in another section, they'll move it.

That is very helpful to know, thanks!

byrantrv.com has a diagnostic service manual for the Duotherm AC units that will help if you have that type AC unit.

Fan speed is typically controlled by a resistor or through a control  board.  It is also possible that the motor has separate windings for each speed,  In any case you'll need the manufacturer and model number to find the correct wiring diagram or diagnostic manual.

Good luck!

John From Detroit:
120 volt fans typically use the multi-winding method.

Possible issues
Bad relay (The clicker)
Bad wire/connection
Bad low speed winding

Suggestion:  Many people report issues with A/C icing up when run on LOW.. Do not use LOW. Use High, that's what I do. Even though low works (I do admit to using LOW fan from time to time.. Just fan not cool)


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