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Duo Therm Heat Pump Repair Problems

Posted by artbalog, 21 May 2010 · 1,674 views

I have a 2003 National Islander with two Duo Therm heat pumps and have not been happy with the performance of the units. I contacted Holland Motorhomes in San Diego about service on the units and the service writer told me that if the units are low on refrigerant, the units cannot be recharged and will have to be replaced. Not beleiving that Dometic would put out a product that could not be re-charged, I emailed Dometic with that question. Dometic customer service got back to me and without giving any reasns, said they do not recommend re-charging their units and suggested where to buy new units. This sounds like a crock to me! We are able to re-charge the A?C units in our homes and our cars but, can't in our motorhomes? Has anyone had the experience on servicing the Duo Therm heat pumps in their coaches?

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I was told the same thing from my RV dealer here in tucson, that they are sealed units.
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I can't address specifically as to if your units can or cannot be recharged; but many years ago I had an old refrigerator that did not have a port to recharge. The old maintenance guy I called told me that there was a clamp on device which went over the suction or low pressure side that had a tip on it to screw on the line for the freon bottle. That was 30 years ago and I don't know if that is still an option or not. Good Luck!
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Your units are sealed! Almost 99% of the time if the unit has not been damaged it just needs to be serviced. IE. CLEANED. The freon dos not wear out so the only problem is that the coils inside and out get dirty and the units efficiency drops. So just a good cleaning should take care of the problem.

Good luck and let us know how it comes out.

Barry
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I contacted Holland Motorhomes in San Diego about service on the units and the service writer told me that if the units are low on refrigerant, the units cannot be recharged and will have to be replaced.
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If the units can't be recharged it is doubtfull that the freon can be checked. I doubt that the service tech knows that it is low. the problem is probably the compressor. I have experienced this in the past and it was better to replace the unit.
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These Duo Thermo Heat Pumps have a reverse switch/contact ?? that operates from air to heat and visa versa . This switch/contact can get stuck . Some stimes by putting the air on for a short period and shutting down for a short time and back to heat may help if it is a sticky switch/contact . Try this if you have not already replaced the unit . These units can not be repaired other than a good cleaning . Use a spray foam cleaner ; should be available at a good havac center . After removing the shroud on the roof , spray fins and any area that crud appears . Rinse with hose being careful not to flood that area of the roof , for otherwise water will come thru the ceiling inside . Clean or replace air filters inside . Been their , done this . or you will have to replace the unit as these are throw aways . Can be replaced yourself if you are some what handy , not a major project but time consuming. GOOD LUCK
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Duo Therm AC units are sealed units and cannot be charged without modifying the unit. One major problem they have been having is a 1/8” capillary tube that sits next to the compressor. If this tube is to close it will result in a hole developing in the tube due to vibration of the compressor. This is hard to detect and the loss of gas can only be verified by checking the load on the compressor. If the unit is more than a year old it was probably made in Mexico where most of the problem units came from. As of last year Duo Therm started getting the units from China so the problem may be resolved.
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As a Master Certified RV Technician, once you break that vacuum of the system, you introduce moisture into it, and corrosion will start, now, a trained AC repair tech, if he takes the time necessary (about 4 hours minimum, and longer is better) can vacuum down the system, add refrigerant/lubrication to it, but being as they are both 8 years old, he will have to add a special fitting (two of them actually) so he can open the system properly. Make sure if you go this route he uses the “solder on” type, as they will seal better. In one post, it was mentioned they might not be able to be charged, if that is the case you need to replace them. And that might be a better thing if you just replace them, the labor should be cheaper, at any rate. Make sure you use a qualified shop or tech. If you are on the west coast, call Kustom Coach Works, ask for Bobby and see what they can do for you. Between the owners they have 25 years experience, and do excellent work. Contact: 541-501-3371. Or you can live with what they do now. FWIW#1 – Heat pumps don’t work for beans below 50 degrees outside temp, and the best “Delta T Split” heat/cold you will get out of an RV or Car AC system is twenty degrees +-3 (average-some better-some worse), which means, if its 50 outside, you might get 70 or a little better for heat, if it’s 90, you might get 70 or a little better on cool. Below 50 you are wasting your time and energy. Carrier used to make the best RV units, but the EPA's new requirement for coolant, they left the market, because it's costs was not in line with the profit needed, and about that time the marked in RV's crashed.

FWIW#2 – all RV systems need to be exercised or used each month for two hours to make sure they are working. Here is how I do it in my MH, I start the Genset, turn on the Aqua Hot, dial up some heat on the zone thermostats, and let the coach start to warm up. I then let the coach get to 75-80 inside. I then turn off the heat side and switch over to AC, and cool the coach down to 60-65. Then I switch from cool to heat on the heat pumps, and let the coach get warm up to 70-75 again. By the time I have done this, I have also charged the batteries, exercised all the house systems, turned on the TV’s, stereos, etc and let those run again. In winter if we stay home, I take it on a 25 mile drive every 45 days, to get the condensation out of the tyranny and engine oils. When I return, I level the coach and extend the slides and then retract them, and unlevel it. Since I’m old, I have used the facilities once and that means turning on the water pump and cycled some water in the coach. If we are on the road, all the systems get exercised, so then I just need to let the BH go shopping and then run the genset. Doing this monthly keep all the systems working well. Since we move about every 3 weeks the HWD system gets worked, and every other time, I clean off the leveling jack shafts so the polished surface is clean. This is especially true of AC/HP units, as those need to run to keep them working properly.Australia
And no, based on what experience I have an Chineese Products, I don't believe the product quality is any good, our chinaeese made coffee pot broke yesterday, and it's two years old, mostly crap quality on china.
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