Second AC freezing up

clay1969

Member
Just installed a Dometic non-ducted, 13,500, low profile AC in MBR. It has froze up 3-4 times on me to the point I can barely here the fan blowing at all much less blowing anything into the cabin. The installer told me that the unit has to 'cycle' since it has no thermostat and to put the dial on half or three quaters so the compressor can cycle on/off and to put the fan motor always on high. Well last night left the dial on all the way and froze up again. I then turned the ac dial all the way off to shut the compressor down but let the fan still run on high thinking it would thaw quicker. Well it did. About 30-45 minutes later, water was dripping pretty fast onto my bed! I'm assuming I should have shut the unit completely off b/c I guess the fan thawed the coil and blew the condensation off the drip pan and down to my bedroom. Am I correct or is something wrong with the AC unit? Maybe to much factory charge causing it to freeze up or me not operating it like i should?
 

Bob&Patty

Founders of SoCal Chapter
Too much charge would make it not cool. Running it on the High fan setting should help with the freezing up issue. A frozen evaporator will shut down air flow. You might have a problem with the compressor cycling switch or what ever they use to control the compressor run time. The compressor has to have something that looks at pressures or temperatures so it does not go below 32* on the low side. Anything below that, for any long length of time, the evaporator will freeze up. Best answer I can give you. I don't know if it is possible to hook a set of A/C gauges to the unit and check the operation of it. JMHO
 

TXBobcat

Fulltime
My Dometic does the same thing. When it starts to frost up you can tell by the way the fan sounds. I turn the AC over to just high fan and it gets rid of the frost and does not drip on our bed. I will turn the thermostat knob to about 2/3 to keep it from frosting up. I wish it would not frost up but I don't know how to stop it other than not turning the thermostat all the way to the right.

BC
 

SmokeyBare

Well-known member
The intake warm moist air side of the A/C unit is separated from the Chilled Air side by way of a thin sheet of metal. I'm not sure if this applies to the low profile A/C unit you have...

The sheet of metal that divided the air "in" and air "out" on the Dometic A/C unit in our Bighorn was/is held in place by double sided foam tape. The tape attachments were failing which allowed the divider sheet of metal to drop down nearly 1 inch. This allowed the chilled discharge air to be sucked back into the warm intake side of the A/C unit. This caused in my opinion the chilled air mixing with the moist warm air to condensate on the coils and then freeze, blocking the air flow. I used some aluminum foil tape (found in most home building centers) to secure this sheet of metal in place, sealing any leakage between the 2 sides of the A/C unit.

Check also for any air leakage inside the A/C unit that would allow the unit from pulling air from the space above the ceiling on the Intake (Warm) side. Check also if there are any leaks on the discharge (Chilled) air side allowing air to flow in the space above the ceiling. I found a few holes, (probably for wires to pass through) and areas where the air could leak in or out. I used foil tape again to seal these areas.

While your looking at the coils, check to see if there is a sensor attached to the coils. There should be a Freeze Sensor attached to protect the A/C unit when a freeze up occurs.

Marv
 

JasonShrout

Member
I have a similar problem with mine as well, except it isn't dripping inside. Even when we have the ac off, the compressor cycles until it freezes up. I popped off the top cover and didn't see anything amiss, even under the cover for the compressor. It didn't do this when running from the generator, only on shore power. Is there a relay hidden somewhere?
The thermostat doesn't look damaged and I can't find any bare wires. I'm worried that if we don't keep the ac on full blast, damage will occur.
 

danemayer

Well-known member
Not specific to RVs, the most common causes of A/C freeze-ups are low freon levels and clogged filters.

Despite that, on these bedroom units, if the unit is not too old, I'd go with Marv's advice first and check for air leaks inside the unit.
 

jimtoo

Moderator
Also on all the rv units and very common for freeze ups is the temperature sensor that clips onto the evaporator fins falls off and is just hanging there. It can be seen by removing the inside cover where the air filter is, might need to remove complete bottom cover, and look up into air intake area on the fins and see if a small sensor, nickel or quarter size, is attached to fins. It will have 2 wires going to it.

Jim M
 

Birchwood

Well-known member
I had a dometic 13500 installed on the front in January of this year We used it in March and April in south Florida
and never experienced a freeze up.It works great other that the high noise level.It will haul the bedroom temp
down to 65 F in no time.They have a 2 year warranty so Dometic should look after the freeze up problem whatever
is causing it and you can be sure there is a fault as freeze up is not normal.
 

Sandpirate69

Well-known member
I heard about the Dometic issues, so I put a Coleman in mine. Infact im thinking about replacing the main A/C with a Coleman Mach III 15K which puts out an extra 90 cfm.
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
We've had the freeze-up overnight. But it's hard to recreate, so we've delayed having it looked at. Thanks to this forum post, I have an idea where to start to look at it. ;)
We've not used the 2nd air enough yet this season to have the freeze-up happen, so far.

Erika
 

JasonShrout

Member
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Just an update... I wound up having to tear out the control board.
Tracing the freeze up connection on the board back to the relay, unsoldering it and tearing the relay apart, found it to be stuck in the open position.

I cleaned up the contacts and put some electrical lubricant on there for safe measure.
Superglued the housing back together, soldered to relay back on the board and reassembled it. Works great now!!
When I get to my computer, I'll post the pictures.
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This tapatalk is awesome. :)
Since my initial post on this, the unit is still functioning flawlessly.
 
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cookie

Administrator
Staff member
Good to hear that your repair held up. I suspect it will not be a problem in the future.
This is something I will keep in mind should I have any unexplained freeze ups.

Peace
Dave
 
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