Cooled perfectly yesterday. Turned it on today--no-go. Voltage in the TT is 120-122. 1500w microwave works fine with very little voltage drop, so I'm assuming incoming power is fine. For the heck of it I did try the 50a outlet, too---I still get the same symptoms:A/c unit is non-ducted, with all controls and vents in the ceiling console. Fan works fine on all 3 speeds, but there's no cooling. With the fan on high and the thermostat set for maximum cool, something in the a/c is trying to "cycle" every 30-45 sec. for approx. a second--continuously, every 30-45 sec. When it does, voltage in the TT drops from 120 to about 114 for about a second. You can hear the a/c fan and another fan I have turned on change pitch slightly every times it cycles. Must be quite a bit of momentary current to drop the voltage like that--I'm estimating 20-25a.I'm camping right now, with plans to depart tomorrow morning, so don't have a ladder or any test equipment except a VM. Bad start cap? Bad compressor? Any recommended tests/checks on the upper unit (or ceiling console) when I get home tomorrow?Mucho thanks!P.S. PI EMS has been on 24/7--no errors reported.

Voltage drops from 120V to 114V because A/C Unit compressor motor is bad

Hi,Yes the compressor might be bad. Or the capacitor. Because you can buy a 35 Mfd capacitor for about $20, you might as well replace it, and see if the compressor starts.Of course if you know how to use a volt meter, you can ohm the compressor terminals from one terminal to ground (with the RV unplugged) and if you get resistance, then the compressor is bad, and you can not repair it.Replacing the compressor is 'possible' however a 12,000 Btu compressor will run me around $400, and you are looking at about 6 - 8 hours labor, $40 in freon, $40 for a freon drier, and a 90 day maximum warranty on the replacement compressor. This is why they are called 'non-repairable' because a new unit with a 5 year compressor warranty is around $700 - $800 and sometimes places like Camping World will install them for a low cost (say a $5 installation sale special). Good luck, and hopefully it will be a bad capacitor! If you keep turning it on, then it will be a bad compressor very soon! I hope that you did not let it cycle on and off for more than a couple of minutes. It is very bad on the compressor (assuming that the capacitor was the only thing wrong with it to start with).If the compressor is shorted to ground with say 100 ohms or less to ground, then it is really bad burnt up motor winding, and not worth trying to repair, even if you got a compressor for free. A low ohm short to ground is very acidic, and all that acid in the tubing will quickly start eating away the new compressor motor windings. Fred.

Start with a new start capacitor... a common problem. It's the bigger of the two you will find. Using a screwdriver short the contacts to ground before removing.

Agree with Capacitor First. If the Capacitor is bad, the Compressor will draw LRA (Locked Rotor Amps) like a stuck one.Your brand MAY use a two-way capacitor. A Fan terminal, a Compressor terminal (likely marked HERM for Hermetically sealed system), and COM, Common, probably between the other two. IF that's so, and FAN runs, you only need to buy a single capacitor with the higher of the two uF (maybe marked MFD) values, 35 in Fred's example. Just ask for a jumper to connect the COM of the two-way to one terminal of your new one and of course move HERM to the other terminal. So you may find only one "can" in there. If you find a tall, round, plastic capacitor, a third one, let us know.

Dometic 13.5k a/c Inop | Good Sam Community

14 Replies

Ivylog
Explorer III
Nov 01, 2015
Start with a new start capacitor... a common problem. It's the bigger of the two you will find. Using a screwdriver short the contacts to ground before removing.
Golden_HVAC
Explorer
Nov 01, 2015
Hi,

Yes the compressor might be bad. Or the capacitor. Because you can buy a 35 Mfd capacitor for about $20, you might as well replace it, and see if the compressor starts.

Of course if you know how to use a volt meter, you can ohm the compressor terminals from one terminal to ground (with the RV unplugged) and if you get resistance, then the compressor is bad, and you can not repair it.

Replacing the compressor is 'possible' however a 12,000 Btu compressor will run me around $400, and you are looking at about 6 - 8 hours labor, $40 in freon, $40 for a freon drier, and a 90 day maximum warranty on the replacement compressor. This is why they are called 'non-repairable' because a new unit with a 5 year compressor warranty is around $700 - $800 and sometimes places like Camping World will install them for a low cost (say a $5 installation sale special).

Good luck, and hopefully it will be a bad capacitor!

If you keep turning it on, then it will be a bad compressor very soon! I hope that you did not let it cycle on and off for more than a couple of minutes. It is very bad on the compressor (assuming that the capacitor was the only thing wrong with it to start with).

If the compressor is shorted to ground with say 100 ohms or less to ground, then it is really bad burnt up motor winding, and not worth trying to repair, even if you got a compressor for free. A low ohm short to ground is very acidic, and all that acid in the tubing will quickly start eating away the new compressor motor windings.

Fred.
Old-Biscuit
Explorer III
Nov 01, 2015
Voltage drops from 120V to 114V because A/C Unit compressor motor is bad
otrfun
Explorer II
Nov 01, 2015
Oops, double post :(

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Dometic 13.5k a/c Inop

14 Replies

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