Question about Dometic Rooftop RV Air Conditioner

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Dometic roof A/C fan

The fan will not start up with the A/C, not even if I select the fan only position from the selector switch. I can hear the compressor kicking in in the cooling mode. The fan is free to the touch. If i spin the fan slightly and select the switch the fan runs in cooling or in the fan mode in all three speeds. My finding is that the fan does not or canno start on its own. What controls the stating function of the motor.

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  • olmac Jun 19, 2008

    Hi Thank you fort he help, but as I mentioned before the fan will run as usual on all three speeds if I give it a spin to start it up. But the fan will not start up from a dead stop. Once the unit stops after raching the thermostat setting the fan deeds another push. I have two capacitors, larger one and another small one with a starter on top of it which shows some signs of brown colour. So can Iassume the motor is still in good shape and the capacitor is diffinitly the problem here.



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If the fan motor is humming when you turn on the fan switch and it seems like if you spin the fan, it wants to try to spin on it's own but can't-your problem is the run capacitor. This will be a small round or oval cylinder that connects to the motor with either two or three wires. On the side of the capacitor should be a label or printing the size of the capacitor is rated in microfarads which is indicated either uF (the u will have a little tale pointing down on the left side) or MFD. Match this up to a new capacitor of the same size. Voltage rating of the capacitor is not important as long as it is 370 volts or higher. When you hook up the new capacitor, which terminal the wires hook up to is not important HOWEVER, if there are two wires going to one of the terminals, those two wires must stay together and go to one of the terminals together on the new capacitor. If you follow all of these instructions and the motor still does not work, then the motor has failed internally somehow and will have to be replaced. Whenever you replace a motor, ALWAYS replace the run capacitor that goes with it.

Posted on Jun 18, 2008


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