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Old 02-16-2016, 07:07 PM   #1
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A/C unit won't kick on and produce cool air

Hi, I have a Dometic 13.5K A/C unit in my 2013 Forest River SV305 Surveyor. When I turn on the unit and set the proper temp to cool on a warm day, it hums like it wants to start and run, but nothing actually runs. It never blows air? I took the A/C lid off on the roof and I don't see anything loose or broken. The fan blade spins freely by hand? Also, all fuses are fine and wires appear connected under the roof cover and above the filter inside?

Any idea on what might be causing my A/C to not kick on?



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Old 02-16-2016, 07:25 PM   #2
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First suspects would be the motor capacitor or voltage drop in the circuit.

Test the capacitor by substitution, test the voltage with an AC voltmeter.

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Old 02-16-2016, 07:45 PM   #3
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I would suspect the unit needs to be replaced. Dometic has had their share of issues with units loosing their charge. I only got 1 year out of mine
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Old 02-17-2016, 07:32 AM   #4
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I agree with BluePill about it probably being the capacitor. The blower and compressor share a capacitor so if one side is bad the other probably is also.

As a test you could try to spin the fan blade by hand as someone sets the T-stat on. If the fan runs then it's the cap.
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Old 02-17-2016, 10:02 AM   #5
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Agree with others, more than likely the capacitor. Since your unit is a little older it does likely share a start capacitor. Many times you can look at the capacitor and see burn marks or deformity on the top or bottom, if this is the case probably bad. If it is the capacitor suggest you up grade and install a Supco capacitor that has a little more umph and will better start the AC from a generator if needed, also much less stress on the compressor.

There is the possibility that there are two capacitors make sure you check the line voltage, if this is really low the unit may not start even with good capacitors.
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Old 02-17-2016, 10:13 AM   #6
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Look for swollen capacitors. You can check them with an ohm meter. Be sure and discharge them first with a screwdriver. I think the domestic starts the fan 1st so I'd look hard at the fan capacitor. If you can get someone to turn the ac on while you are on the roof, you might hear the fan motor humming. I'm not tell you to do this but sometime a spin of the fan in the right direction will act as a capacitor and it will take off. I vote fan capacitor. Compressor would probably trip a breaker. But you need some more diagnostic. It's likely a $10 capacitor. Don't junk the unit yet.
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Old 02-17-2016, 11:46 AM   #7
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Perhaps you need to check AC breakers. If 50 Amp, both phases should have power.
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Old 02-17-2016, 12:37 PM   #8
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We bought our used wildcat a few weeks ago and the ac unit didn't work when we checked it out. Colerain Rv said it was a capacitor and fix along with a few other issues before we signed and picked it up. Unit would not fire up when put in cool mode,hope this helps.
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Old 02-17-2016, 04:34 PM   #9
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Had similar issue with my Dometic and it was the capacitor. You could hear the compressor try to start momentarily but it would kick right off leaving the fan blowing warm air. Of course this happened at the start of a July 4th trip that coincided with a heatwave!
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Old 02-17-2016, 04:59 PM   #10
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I agree with Davel1971 - We are on our 3rd AC - Dometic has issues!!!

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