A/C Evaporator Icing NEED HELP

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J

jahmes143

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Apr 18, 2017
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7
Dometic 15k, ducted, on 2015 Cougar XLite 31? 5er.

My evaporator is forming ice on the top inch or 2 (see pic).  Forms within 15 minutes and doesn?t get much worse.  System ran for about 4 hours and only cooled the trailer from 88 to 86.  Trailer is sitting in full sun, 80 degrees outside, 80% humidity.  Turn the system off and pretty instantly the ice melts and a quart or so runs off the roof.   

Fan/condenser function properly.  Fan is set to HI and there is lots of airflow thru all ducts.  Temp at ducts is about 65 degrees.  All coils/filters/etc are perfectly clean and the box is fully sealed (no air escaping from supply into the return). 

I know the unit won?t cool the 5er instantly, but 2 degrees in 4 hours seems rather bad.  My question is mainly about the icing on the evaporator though.  My understanding is that if functioning properly THERE SHOULD NEVER BE ICE on any part of the evaporator.  Is this correct? Since I know it?s not an airflow issue, is the only other possible problem low coolant level??
 

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My guess with 65 degree output and freezing evap:  Restriction of Freon somewhere in system. Don?t know if that unit has a office tube or a expansion valve, but would bet something is partially plugged.
 
All rv units are capillary tubs, if that's the way it frost when its together so the fan will move air over the coil then its short of gas or the compressor isn't pumping right.

Denny
 
20 degrees differential across the evaporator is good.  The fact that there is a bit of ice forming on the evap is an indication of a slight problem.  I know you said that filters were clean, fan is running correctly and the evap is clean also, so to me, there is a couple of possibilities.
1.  A slight loss of refrigerant in the system.....which would indicate a leak somewhere.
2.  For some reason, that small section of the evaporator with the ice forming on it, isn't getting enough air flow across it.  Double check to make sure that the enclosure is completely enclosed and that there is no possibility of escaping conditioned air from the evaporator enclosure.  If that part looks to be OK, it might be time to try and find a slight pin hole/bad solder joint and see if you can locate a freon leak.  It might be so small that you cannot see/detect it without soap bubbles or a freon sniffer.
 
xrated said:
20 degrees differential across the evaporator is good.  The fact that there is a bit of ice forming on the evap is an indication of a slight problem.  I know you said that filters were clean, fan is running correctly and the evap is clean also, so to me, there is a couple of possibilities.
1.  A slight loss of refrigerant in the system.....which would indicate a leak somewhere.
2.  For some reason, that small section of the evaporator with the ice forming on it, isn't getting enough air flow across it.  Double check to make sure that the enclosure is completely enclosed and that there is no possibility of escaping conditioned air from the evaporator enclosure.  If that part looks to be OK, it might be time to try and find a slight pin hole/bad solder joint and see if you can locate a freon leak.  It might be so small that you cannot see/detect it without soap bubbles or a freon sniffer.
Click to expand...

In the photo so just the first coil frosting with no air over the coil, if it had a full charge of gas it would frost all the way down and to the compressor on the suction line (the bigger line) in a very short period of time. So it's almost out of gas or the compressor is bad. The only way to tell is tap the system with access valves and use a set of gauges, if you have to pay some one its usually better to just replace it.

Denny
 
Thanks for all the replies so far.  I'm thinking there must be a slight leak somewhere.  I hadn't heard of a bubble test before.  I'll give that a shot.  On an amp meter, the compressor read 8.5 amps.  It's rated to 13 something I believe.  Is that too low? From what I've read, that might also indicate a leak?? The compressor tested 118 volts. 

What's odd is that I'm still getting about a 15-20 degree differential, yet the interior temp of the trailer is staying 85-88 degrees.  I even pulled 2 of the 3 slides in, tinted windows, and made sure blinds were shut.  Maybe the Cougar Xlites have sub-par insulation (R7 on the walls, not sure about the roof). 

I do have a bullet piercing valve, but the cost of the r410a refrigerant is crazy...like $100 a bottle. So I'll likely end up just buying a new unit.  Amazon has them under $600
 
It may he worthwhile to contact Dometic. Who knows, there may have been a recall on certain machines. It's only 2 years old which is just barely broke in.
 
Rene T said:
It may he worthwhile to contact Dometic. Who knows, there may have been a recall on certain machines. It's only 2 years old which is just barely broke in.
Click to expand...

Yes and not used for more than 15 days total! Maybe it was low filled from the factory.  I spoke with Dometic.  They advised there were no recalls/issues with my model, offered a few basic diagnostic suggestions, and told me to take it to a dealer. 
 
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