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Old 08-14-2018, 10:18 AM   #1
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worthy420's Avatar
2007 25' Safari
Cranston , Rhode Island
Join Date: Dec 2015
Posts: 18
Wink Losing your "Cool" with Dometic DouTherm?

Hey Folks,
I want to share an important discovery that as someone new to RVing could have cost us $1200 or more, had I not done my own investigative work.

I suspect that we're all putting our AC systems to the test this summer season - and like many of you - found mine running just fine one minute and then all of a sudden no longer cooling the cabin - ugh!

My first instinct (2006 Dometic 13,500 but Dou Therm AC unit - was just replace it! But the price gave me pause. . . and the motivation to do some quick research.

Let me get to the point - most RV centers do not service older units (either lack the expertise or figure that it's a dis-service to the customer because of labor cost vs age of the unit.

But as I discovered (Fan/thermostat worked normally, but compressor would not start or tried to start but repeated-ly "kicked out." Of course, proper electrical supply was my first check ( 30AMP 110 Volt) Fact: If you have lost your electrical potential - your AC unit will not start (this is a built-in safety) but if you can substantiate a proper electrical connection as I did - your next likely problem is the "motor start - capacitor" Folks this is a approx. $30 piece of equipment which can be ordered online through many places (

Installing it required me going on the roof with some degree of common sense and a safety precaution (Fact: capacitors can give a Hellava shock) To discharge a capacitor you use insulated screw driver across the terminal (see youtube). But it not my intention to give instruction here - but to let you all know - its a cheap and relatively simple fix and one that often does not get recommended to unsuspected/inexperienced RV owners.

On my AC unit I have two capacitors #1 is the fan motor capacitor and the #2 secondary one is the Motor Start capacitor. One is connected to the other. Therefore if you don't have a working fan. . .then you may need both capacitors? Both cheap fixes, when you compare it to the alternative. Hint: see youtube for help in further understanding this problem and suggestions or email me back and I will try to guide you further. I suspect there are potentially thousands of you with the same problem I had and with potentially $$$$ to save.

BTW: my AC is working like a champ and while I had the cover off - I did a little house cleaning (condenser-coil) Oh. . my wife gave me the high-five on this one! I need all the "points" I can get. lol

I hope you find this helpful

Peter W

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Old 08-14-2018, 11:12 AM   #2
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2008 23' Safari SE
Houston , Texas
Join Date: Aug 2014
Posts: 78
thats the same unit i have on my 2008 23FB. i'm having some work done on the trailer and the worker called me a couple weeks ago and said your A/C stopped working. he tried changing the capacitor but he said it wouldn't stay on. turned out to be the thermostat. I want to know how you knew your thermostat was working fine?

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Old 08-15-2018, 10:53 AM   #3
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2007 25' Safari
Cranston , Rhode Island
Join Date: Dec 2015
Posts: 18
Hi Rocket,

As I am not a technician - I can not say for sure. . . however I made the assumption because the Thermostat "appeared to functioning as normal" - for example. . .when I raised and lowered the settings of the Thermostat - the AC unit attempted to start . . .thou unable due to the malfunctioning capacitor. If you remember from my original post that my fan worked fine and I could control the speeds as well from the Thermostat.
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Old 08-15-2018, 01:03 PM   #4
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2014 25' International
2006 23' Safari SE
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Boulder City , Nevada
Join Date: Aug 2007
Posts: 2,965
Peter... good post!

Lewster, who follows the Airforums provided me with the same information of replacing these capacitors, and maybe a resistor, in our 2006 23 footer's AC Unit.

I was able to take the parts, solder them and took care of the issue. A great reminder finding your Thread. You will be able to smell the 'can capacitors'. Replace both. They are relatively inexpensive.

At Sam's Town Casino RV Park in Las Vegas, NV they had a power surge and took out a number of AC's at the park. It was not Dometic's nor Airstream's fault.

My first instinct was to do a 'modification' to the AC, but Lewster stepped in and provided parts at a reasonable price and an easier way to make the repair.
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