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Dometic Duo-Therm 15KBTU A/C - Freezing Up Issue

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Silver Hawk

RVF Newbee
Joined
Feb 13, 2020
Messages
3
Location
Sarasota, Florida
RV Year
2004
RV Make
Dutchmen
RV Model
31 FKDS
RV Length
31
TOW/TOAD
10,000
I can't be the only one with a Dometic Duo-Therm 15KBTU A/C Unit that invariables freezes up when the outside air temp drops to about 78 degrees F or 75 degrees F. The unit runs wonderfully! If it's 80 degrees F and hotter, it is a flawless unit! But SO often, I go to bed, at night the temp drops, and if it gets to about 75 degrees F outside . . . I am waking up to find the A/C not working, because there is a 1/2" of ice on the coils. I have to turn it off, let is 'thaw,' and hope for the best in turning it on again. I HAVE to believe I'm not the only one? I called Dometic - they were very nice. They explained - essentially - that this was 'normal.' "Why would you need A/C at 75F anyway?" Because I'm in Florida, it's 95% humidity outside, it might be raining . . . because I want the A/C running while I sleep! That's why! They seemed to find it acceptable that outside ambient air of a temperature less than 65 degrees F was going to cause the freezing up - and they seem to think this is 'acceptable!' But again, I'm having issues at 75 degrees F.

I do not have a heat pump. My model is: 59516.711 It was original/new in 2004.

Things I should mention: I found the freeze control sensor literally JAMMED into the coil fins. It's apparently supposed to 'snap' onto one of the evaporator lines. I snapped it onto one - not sure if it's in the right spot - but it does not seem to have made a difference. Also, I'm not terribly confident that they 2 wired from the freeze control sensor are making a connection to the 'hidden from view' circuit board. I wonder is someone may have intentionally disconnected it?

Also, there seems to be a lot of chilled air leaking from the 'pressure side' back into the 'intake side.' Whatever was creating a seal between the intake side and the 'pressure side' (from where the air ducts receive the freshly chilled air) seems to have deteriorated, and again, there seems to be a lot of the freshly chilled high pressure air that should run through the ducts, 'escaping' back to the air inlet side. I don't know how big a problem this is? Or if this is what may be causing the icing up?

I should add that the previous owners had the ceiling vents (that you can turn to direct the direction of the air) REMOVED. I replaced them. I wonder now if they did that because there was an inadequate flow of air - and that was causing freezing for them (I got the 31' Dutchmen FKDS from a dealer and never met the prior owner).

If anyone has ANY suggestions or advice, I would VERY sincerely appreciate it.

Dave Williams
 

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Generally a hard clear ice on the evaporator means the drain is plugged and a white frosty coil means there is an air flow problem (not enough). Try checking the drain pan at the bottom of the coil can drain all the water away. It could be draining slowly and with the heat load inside dropping it allows the ice to accumulate. Another possibility is the unit is slightly low on the refrigerant charge, doubtful, but a slim possibility.
 
was gona say air flow.
 

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