Question about Dometic Rooftop RV Air Conditioner

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I have a 5th whell RV Couger 2006 had 1 AC unit replaced already now two years later it only pumps slightly cooler air but has condinsation streaming off the roof. An hour and a half later the interior is still up at 90F so I assume the AC need charging but I'm told it is a sealed unit so they would need to re-place it with a whole new unit.

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  • Mike Solon Sep 02, 2010

    I just got the 5th whell back from the dealer which I had an extended warrenty with and they replaced the entire AC unit stating the AC had a leak and had to be replaced. They also replaced the wiring down to the fuse box and my two awning end caps all under the warenty. Why would the AC unit devlop a leak in just two Summers uses? I leave it plugged into the house and set the thermostat to 80F and let it run, is that over use of the system?



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Yes it is a sealed unit, and there are some refrigeration guys who can solder on valves and recharge, but make sure you get a quote first, as some charge as much as a new unit. That said, I'd be looking at evaporator coils/fins as well as condenser coils and fins for dirt and debris and give them a real good cleaning. I'm going to assume this is a ducted ceiling, so Make sure your getting flow through all those ducts, and check for how cool it is. Does it feel like cooler air coming out the ducts? Rule of thumb is 20 F difference between ambient and discharge should be normal. All that condensation tells me it's trying to cool but you may have a problem elsewhere, like plugged fins, or faulty ducting. If the flow coming out of ceiling ducts is not good and cool, try removing the ceiling assy and see if the discharge side is cool there, and check that the ducts in to the ceiling have no obstructions as well and are properly aligned.Let me know what you find. Make sure return air filter is clean as well and get a flashlight and look way up in the return area, at the fins for dust collected on fins etc. If you remove outside cover on roof, turn off breaker, and you can use a hose to spray down and a nylon brush to clean fins and coils at condenser. Watch for bees, or wasps when you remove that cover on the roof.

Posted on Jul 30, 2010

Testimonial: "Very helpful I did find the filter very dirty but cleaned that and still no cool air but I plan to check the intake area with flash light as suggested"

  • Mike Butler
    Mike Butler Aug 01, 2010

    Don't be afraid to remove the plastic ceiling assy, so that you can feel the temperature of the discharge side as well, and you should also feel where divider is between return air, and discharge side for leaks coming through from discharge to return side. You'll feel cooler air coming across to return side if there is any leaks, tape them with foil tape, or even duct tape if nothing else available. When you expose discharge side by dropping ceiling assy, feel the temperature of the air, and if it feels good and cool, then you know your problem is in the ceiling duct work, or inlets to it, and changing the rooftop assy, wouldn't cure your problem. When you drop the plastic ceiling assy, there will be 4 bolts holding from inside bracket to rooftop, don't remove them.That's what holds them together, and secures rooftop to inside ceiling. You can usually remove all the screws holding inside plastic assy to those brackets, and usually a few holding metal tray with wiring and let it hang by power wire carefully, to test it. There is normally a tin/galvanized short divider mounted to tray that separates return, and discharge. Keep me posted what you find for temperature difference there.



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