Hey all...don't know if this is the best section to post this question but seemed like a great place to start.We purchased a 2007 Cardinal 5th wheel with original Duo-Therm 15,000btu roof air last year and enjoyed the air conditioner all summer...worked great. Turned it on couple days ago and seemed to run fine to begin with. But after several hours the air temperature started to warm a little and progressively get warmer.Before I first started it up I got on the roof and removed the cover and did a simple cleaning. Then turned it on and started working great. The coolant line started sweating as it should and was very cold and the return line was very warm. Ran great like that for many hours. But then several hours later the interior air started getting warmer so I went back up on roof and checked the lines and now the cold line is only slightly cool and not sweating.It almost seems as if I have lost my Freon?? Is there something else I should check? The unit seems to be running fine? I don't see any place to add freon???Appreciate any help....thanks, Phil

There is no place to add freon because they are sealed units and not serviceable. Like a window unit in your house. You basically have to throw this unit away and buy a brand new one if it no longer works because it has lost its coolant or the compressor has failed, or anything else goes wrong.

Are you sure it is not just icing up?

Might be, "freezing up." Start by cleaning the fins up top and certainly pull the foam filter out and wash and dry it. It will be just inside the main vent cover on the ceiling.Similar to this:

I'm not an expert but you should check to ensure you have a clean filter and that the evaporator is not froze up. Often these can freeze if not ran on high fan. Best results come with AC on high and fan on high. Also setting it for the fan to run all the time can prevent freeze ups which sounds like what yours is doing. For now, turn it off for an hour and run the fan only and restart with fan on high and running constantly to see if it performs as expected. Others will be along to add to these simple troubleshooting ideas.

It does sound like the indoor coil collected some frost, and if the compressor did not cycle off during the day, it might have frozen over. By setting the thermostat a little warmer, it will cycle off once in a while, and the fan will remove any frost, and the coil will not freeze. Yes I have repaired a leak and add more freon to a couple of rooftop units. I have also repaired window A/C units, but it is not low cost. My company charges $150 per hour, so it can be really expensive, a new $750 unit with a full warranty is looking pretty cheap.But you can find refrigerator repairmen who can weld on a fitting on the copper suction line, and then puncture the line, and add freon. Of course if you have a leak that is 1/2 ounce per year, it will only take a couple of years for it to become low on freon again. The system only holds about 1 pound of freon.Good Luck,Fred.

Roof top A/C not cooling properly | Good Sam Community

16 Replies

meleavingsoon
Explorer
May 27, 2016
Thanks so much guys!

I have check and cleaned the interior filter...actually it was pretty clean from my last year cleaning. And when we stopped using last summer there was no evidence of it failing.

I wondered about the freezing up possibility...but I have already shut it down for several hours to give time to thaw but when I turned it back on nothing has changed. If it were frozen wouldn't it have thawed and then been functioning properly??

I did climb back on the roof this morning and touched the coolant line and it was just barely cool. Then I touched the "return coolant line" (don't know the techancal terms :) and it was very hot.

The exterior fins seem pretty clean, no obstructions. The section of the unit that the cold freon runs thru is sealed so I can't inspect it...unless I remove the screws and open my view to it. Should I open that section up and see if it needs some cleaning??
Golden_HVAC
Explorer
May 27, 2016
It does sound like the indoor coil collected some frost, and if the compressor did not cycle off during the day, it might have frozen over. By setting the thermostat a little warmer, it will cycle off once in a while, and the fan will remove any frost, and the coil will not freeze.

Yes I have repaired a leak and add more freon to a couple of rooftop units. I have also repaired window A/C units, but it is not low cost. My company charges $150 per hour, so it can be really expensive, a new $750 unit with a full warranty is looking pretty cheap.

But you can find refrigerator repairmen who can weld on a fitting on the copper suction line, and then puncture the line, and add freon. Of course if you have a leak that is 1/2 ounce per year, it will only take a couple of years for it to become low on freon again. The system only holds about 1 pound of freon.

Good Luck,

Fred.
fla-gypsy
Explorer
May 27, 2016
I'm not an expert but you should check to ensure you have a clean filter and that the evaporator is not froze up. Often these can freeze if not ran on high fan. Best results come with AC on high and fan on high. Also setting it for the fan to run all the time can prevent freeze ups which sounds like what yours is doing. For now, turn it off for an hour and run the fan only and restart with fan on high and running constantly to see if it performs as expected. Others will be along to add to these simple troubleshooting ideas.
downtheroad
Explorer
May 27, 2016
Might be, "freezing up." Start by cleaning the fins up top and certainly pull the foam filter out and wash and dry it. It will be just inside the main vent cover on the ceiling.

Similar to this:
Jack_Diane_Free
Explorer
May 27, 2016
Are you sure it is not just icing up?
mkirsch
Nomad II
May 27, 2016
There is no place to add freon because they are sealed units and not serviceable. Like a window unit in your house. You basically have to throw this unit away and buy a brand new one if it no longer works because it has lost its coolant or the compressor has failed, or anything else goes wrong.

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Roof top A/C not cooling properly

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