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Randall
Randall, RVIA Certification
Category: RV
Satisfied Customers: 10327
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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Have a rooftop A/C issue. Unit won't start. Both A/C and

Customer Question

Have a rooftop A/C issue. Unit won't start. Both A/C and control are working. Have power to fan and compressor. Does fan circuit have to be running for compressor to start? Unit always starts fan first, then compressor. Is there a way the control board measures for fan operation (current draw, etc.) then tells the compressor to start?
Submitted: 1 year ago.
Category: RV
Expert:  Randall replied 1 year ago.

Yes.....that is usually how it works. What is the make and model of your A/C and the make of your thermostat? Analog or digital? What have you checked thus far? Get back to me with this info and I can assist you further here. All follow up are included in our fee.

Customer: replied 1 year ago.
It is a Coleman Mach 3. Model 48208C879. It has a digital RV Comfort control. The front AC works fine. This one had fan noise before it failed. Replaced the fan run capacitor and compressor start capacitors. The control board clicks when I turn it on. If I go to fan only the fan will not run. I suspect the fan motor has an open circuit.
Expert:  Randall replied 1 year ago.

It might, but the "click" is usually telling......that shows the relay is closing, but probably not passing power over. You can take a small digital multimeter and check it OUT of the relay. A new fan motor may be needed, but even then the compressor will usually come on as that relay controls both. Check that and see. Get back to me if you need more on this later and I will make a phone call option available for you if you think that would be helpful here.