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 28, 2016
j-d wrote:
Phil - I'm glad you did the troubleshooting to find it was leaks. I'm all too much into trying to wring extra life out of things, and it grieves me when folks chuck something I think is salvageable. On A/C, I'll replace Fans, Fan Motors, Controls, Capacitors, stuff like that. But if the problem's in the Sealed System (coils, compressor, tubing, expansion device, filter/drier) it's my time to replace.
I'd suggest a call to PPL Motorhomes 800-755-4775. Give them your current Model Number and tell them what you want to do. Their website invites us to do that.
Kountryguy - PPL's page shouts in RED that there's an issue with Newmar and they know what to do about it.

Thanks j-d ....I will give them a call and see what they suggest.
j-d
Explorer II
May 28, 2016
Phil - I'm glad you did the troubleshooting to find it was leaks. I'm all too much into trying to wring extra life out of things, and it grieves me when folks chuck something I think is salvageable. On A/C, I'll replace Fans, Fan Motors, Controls, Capacitors, stuff like that. But if the problem's in the Sealed System (coils, compressor, tubing, expansion device, filter/drier) it's my time to replace.
I'd suggest a call to PPL Motorhomes 800-755-4775. Give them your current Model Number and tell them what you want to do. Their website invites us to do that.
Kountryguy - PPL's page shouts in RED that there's an issue with Newmar and they know what to do about it.
Kountryguy
Explorer
May 27, 2016
Apparently that depends on the trailer. I have a 1999 Newmar and it requires a special unit to match the duct work. Guess how I know! Good luck.
meleavingsoon
Explorer
May 27, 2016
Thanks guys for all the help....I did find my problem....low/no freon due to a couple of leaks. I'm just going to trash this 10 year old unit and install a new one.

So, do I need to buy the exact same brand and model number to change this bad one out? Or are they very interchangeable?

The bad unit is Duo-Therm model #59516.336 ducted 15000btu
j-d
Explorer II
May 27, 2016
This Thread has some information, a link to Chris Bryant's A/C Tuneup Blog Post, and a Diagram of a typical RV Rooftop A/C.
Once the Shroud is off, the Evaporator Core can be accessed by removing sheet metal on the Front (left in the diagram) end of the unit. If it's a Ducted A/C, with Wall Thermostat, there'll be a Freeze Sensor. It needs to be properly placed and will shut the system down early if it isn't.
Unfortunately, the current version of Chris' post doesn't proper display OR link his photos.
dougrainer
Nomad
May 27, 2016
CA Traveler wrote:
SolidAxleDurango wrote:
Nowhere did any line exhibit the typical sign of leakage... Dirty or oily residue....
To bad he didn't insert some dye as a future leak would then be very easy to detect.

If it was low/empty, YOU HAVE A LEAK. They only hold 1 lb of coolant, so it will not take long for your fixed AC to stop blowing cold. IF he used a clamp on line tap, then you will have another leak in the next year. Line Taps compress the copper line and will eventually leak. They are not meant as a permanent fill valve. Doug
CA_Traveler
Explorer III
May 27, 2016
SolidAxleDurango wrote:
Nowhere did any line exhibit the typical sign of leakage... Dirty or oily residue....
To bad he didn't insert some dye as a future leak would then be very easy to detect.
SolidAxleDurang
Explorer II
May 27, 2016
My main 15K unit in my 2012 trailer started to cool poorly towards the end of last year.... Even began to drip water into the interior when using the "dump" feature.

This unit never did cool as awesome as the 13.5K bedroom unit...

I checked the interior filter - was basically Ok...
Pulled exterior cover and took my air compressor hose to blow out the condenser coils - basically OK as well...
Checked interior plenum for mixing of in/out air... Basically OK, but one spot could use some re-taping.
Checked the exterior box over the evaporator coils - looking for mixing of air... Reaped.

When checking plenum and evaporator coils, found iced up... Could potentially be result of air mixing... But more than likely caused by low refrigerant charge.

Neighbor is commercial heat/air/refrigeration guy... He tested it... Said was basically empty... He charged it (R4) and the exterior line began to sweat and get "beer can cold" like it should.

Nowhere did any line exhibit the typical sign of leakage... Dirty or oily residue.... Has it been low it's whole life? Is there some leak that is somewhere hidden? Who knows.....It's cooling great now., Like it should have all along.

How long will this last? Dunno... But it's been cooling excellently for the last two weeks.
ksg5000
Explorer
May 27, 2016
Everyone cleans the condenser coils but few clean the Evaporator coils which are hidden (use search feature, lots of threads on that subject). Also some AC units have freeze sensors which sometimes come loose and need to be re-positioned. Lastly - always run the AC unit on high otherwise the chances of freeze issues increases dramatically.
mkirsch
Nomad II
May 27, 2016
No refrigeration repair around here will touch the things because they don't have ports on them.

You would need to find an old school refrigeration guy, but they are getting fewer and farther between every year.