Question about Dometic Rooftop RV Air Conditioner

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Duo therm ac problem

My 2004 duo therm quick cool model #59516.331 15000btu air conditioner quit blowing cold air. Somewhat cool air comes out but not enough to cool the RV in the deep south. Dealer tested it and said there is little to no freon in the close system. A friend who owns an AC repair business said to get another unit, that repairs to fix the leak are difficult and it would be better to replace it. What are my options? Do I have to buy a whole new unit, parts of the unit or what? Thank you for the help.

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  • shellycno Oct 07, 2008

    I have a 2004 RV with a 15,000 BTU DuoTherm A/C unit (Model # 57915-531, Serial # 407-35278, Product # 991731776 1VAC 60 HZ 1 PH). The air blows but will not blow cold. I was told it was the capacitor. I changed the start capacitor and the run capacitor and the problem is not fixed. Why is my unit blowing hot air? Do you think there is a factory defect in the 2004 units? This is the 2nd unit I've put on this RV. I had to replace the original unit after only a couple of months. My RV is nearly 4 years old but it seems I should get better service from this unit. Do I need to purchase a third unit to solve the problem? I'm very dissatisfied with DuoTherm products.

  • Anonymous Nov 23, 2008

    The ac was working fine when I parked it this summer... now it doesn't blow cold air....



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Same problem. I have a 2005 on a Rockwood Roo. Worked fine in October 2009. Not working June 2010. Problem is not a freon leak, compressor went bad. I banged the compressor gently with rubber mallet then with a hammer but that did not work. The fan runs, the compressor runs but gets hot. Also no indication of freon moving through system as everything gets warm from the compressor outward.

Posted on Jul 25, 2010

  • Jay Nov 01, 2014

    Revision to this Post: I mis-stated the problem. I did not actually check the Freon pressure at first. There were no fittings and I assumed the system was fully charged. I added low & high side fittings only to discover the pressure was low. I added R22 and fixed the problem. I did not evacuate because the system still had pressure. I also have a problem every spring where the fan blower motor is a little seized up. It won't start spinning of its own power until I spin it by hand. So I remove the top plastic cover to remove leaves/wasp nests/ junk and spin the fan hand until it spins freely. I can't remember if I had to oil it or if it is a sealed bearing.


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I have a coach (2008) with 2 roof top ac units and 1 gas furnace. Zoned 1 and 2. Both units when turned on together or seperatly start the fan circuit, however the compressors do not start, and the blowers shut off after a few minutes. What the hey?

Posted on Aug 28, 2012

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Yes they are a closed system, and most places don't want to be bothered with cutiing the line, soldering in a fitting for refill, and then find out there is a big leak somewhere, that can't be detected until you waste the freon etc. Have you owned the RV since new, and are sure it did work good before? Have you tested the temperature difference ? For example, they are really only designed to remove moisture from the inside air, as well as cool the inside air (ambient) to about 20 degreesF, below the outside temperature. Has the condensor coils/fins & evaporator coils/fins, been thoroughly cleaned recently? If they are plugged, it can significantly reduce cooling ability of the unit.

Posted on Aug 26, 2008

  • 2 more comments 
  • ssalmaxine Mar 26, 2011

    Please answer question concerning factory defect in 2004 units as we have one that has been used less than 100 hours and will no longer produce cool air.

  • Paul Savopoulos May 06, 2011

    Hello motor1258, I'm having similar problems with my duo-therm AC on my RV. One of my problems is that I don't know how to respond to the help I'm getting because i don't know what the parts under the shroud are called. I see what looks like a radiator with fins in it at the front of the unit and another just like it at the rear of the unit and a black bottle roughly the size of a football that gets hot when running. Also, there are tiny dual lines the diameter of a coat hanger that get cold but the black tank gets hot and so does the line coming out of it going to the rear radiator thing. Both the squirrel cage fan and the rear radiator fan work great and a few moments later, the compressor seems to come on (lights dim and sound change) and stays on for quite some time. Only blowing cool air out of my vents on an evening when it was about 68 degrees outside and after an hour or more, still hadn't cooled the coach. There are also some lines that never got cold at all. What's what, in the way of names of these parts AND, do you think my freon has leaked out since the comp doesn't cycle on and off and the black bottle thing gets hot AND the little twin lines get cold? I'm really lost as to what to do and what all these different parts are called. PLEASE HELP!!!

  • Mike Butler
    Mike Butler May 07, 2011

    To: savop 1967. It almost sounds like your problem may not be the AC unit itself, but the installation, or how the cool air is being or not being distributed. There are also a few things that may be affecting it's performance, such as defective/improper duct work, poor insulation in ceiling or other areas of your RV. So I need to ask a couple of questions. Is it a ducted system, which means basically does the cool air blow out the ceiling at various locations, or does it just blow out at ceiling assembly? How old is the AC unit? Has anyone cleaned the unit thoroughly lately, such as Evaporator coils ( fins at front) and condenser coils ( fins at back) ? Do you feel cool air when hot in the day time and you hear compressor kick in? There are some things to look for if it's a ducted system, so I'll wait for your reply to advise you from there.

  • Paul Savopoulos May 08, 2011

    Hey motor1258..... It's a ducted system. I'm guessing it's as old as the coach which is 1992. The compressor DOES kick in and stays on for quite some time. Haven't checked it on a hot day because we haven't had one here in Northern VA since I discovered the problem. Just rain. I only bought the coach a few months ago in the winter and of course, the AC seemed fine the night I bought it but I couldn't really tell. Anyway, a lot of the fins on the front of the evap are bent over and I'll have to get back up there today to check the condenser fins but I'm hoping that with a fin comb, (which I just read about) I can straighten them out and get better flow. Then I'm going to attempt to clean inside the fins with 409 or something similar and wet vac that out. Unless you tell me otherwise. Thanks..... Savop1967


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