I have a 2013 Coachman with 2 Coleman 15k AC units. They were running fine with the fans on high yesterday and last night I came in today at noon outside temp around 90 it was 85 inside and both ACs running both were frozen. I turned them over to fan only and checked the filters and even used my phone to look inside the duct work to be sure it was clear. No problems found. Any idea why both would freeze up on a hot day? Definitely ruined the weekend.Any help would be appreciated.ThanksMike

Constant running with high humidity can cause them to ice up, especially if there is any blockage in the cooling coils. In order to keep them from freezing they need a balance of warm air passing through to keep them from icing, but enough air movement to produce cool air.Turn off the AC for a while then don't turn the thermostat down so low. The compressor ne3ds to kick on and off so en o.o ugh heat allows ice to melt.

Mach 15's? Ours isn't ducted and does NOT have a Wall thermostat. MUST be run with Fan on HIGH or it will freeze up. You should probably do the same. That said, if yours have wall thermostats, they should be stopping the compressor to prevent what just happened.Have you ever cleaned them? If the Condenser coils are dirty, the reduced air flow there will promote freezing of some of the condensate water. Then the ice pack can spread across the coil and cause a full freeze over. Remove the plastic shrouds, then the sheet metal covering the top of the "indoor" coil (properly called Evaporator) on the front end of the A/C units. Clean that coil and the drain pan with the drain holes at the two ends (left and right). Make sure Freeze Sensor is clipped to the Coil.

Freeze sensor may have shifted/fallen off - worth a look.

If you have WALL Tstats, it should NEVER freeze up regardless of how you operate it or the ambient conditions. It has a FREEZE Thermister to prevent it. If it freezes up, either the Freeze Thermister is not installed/correctly or it is defective. To have 2 fail at the same time points to not being installed.IF you have knob roof top manual control knobs, then freezing is a possibility. The only thing you can do is make sure the Condensor and Evaporator are clean and the AC filters are clea. Run the units on HI COOL and back off the Tstat knob slightly from full cold. Doug

Question Where is the Thermosat/fan/mode switch.IS it in the ceiling grill? or wall mounted.Reason for asking.Many Wall mount controlled units have a 'Frost Sensor" that is a thermal sensor stuck right into the evaporator coils. If it starts to ice up the compressor is shut down for a while.Coleman "Local control" (Ceiling knobs) do not have this sensor.How do I know this. ONe is just to my right as I type.. yes it will Ice up The carrier controlled unit in the back (not a carrier A/C but Carrier controls) has a frost sensor so it should not ice.

Coleman AC freezing up | Good Sam Community

time2roll
Nomad
Jul 01, 2018
Yes move the freeze sensor to where you see the frost.
mlj427
Explorer
Jul 02, 2018
I will be going down one day this week to vacuum the coil, pull the inside trim and make sure the baffles that keep the cold air away from the return air are in place and will check the freeze sensor location.
wolfe10
Explorer
Jul 02, 2018
Best to buy an evaporator cleaner (most box stores), put old towels, etc under the duct so you don't get water in the interior and clean the evaporator and condenser from the roof.
mlj427
Explorer
Jul 03, 2018
Talked to the dealer service guy and Coleman’s service dept and they both think that the baffles between the return and output is letting the cold air leak into the return. So I will pull the lower shroud and seal any leaks then clean the coil. I will see how it goes.
Thanks
dougrainer
Nomad
Jul 03, 2018
mlj427 wrote:
Talked to the dealer service guy and Coleman’s service dept and they both think that the baffles between the return and output is letting the cold air leak into the return. So I will pull the lower shroud and seal any leaks then clean the coil. I will see how it goes.
Thanks

Get and use the FOIL CHROME AC tape.,. DO NOT use duct tape. I was going to mention making sure the air box is sealed correctly. One thing tho, your Freeze Thermister wire has debris all over it. That shows your Filter is not installed correctly or it is worn out. The only place dirt can come from is the interior of your RV and the filters stop that. At least most of it. Doug
DutchmenSport
Explorer
Jul 03, 2018
Good point here. When I switched out my 13,500 btu for the current 15,000 it seemed it just didn't cool right. I was disappointed.

I removed the cover inside the camper, took out the air filter and exposed everything and studied it out. The cardboard divider between the intake side and the output side was just hanging and had gaps allowing the intake to suck the out take air before it even had a chance to blow into the ducts or even the center blast.

I used tape for aluminum stove pipe - extremely strong stuff and no second chances with it - touch it anywhere and it don't move again. It's silver color, extremely resilient to heat and cold as it's designed to take heat from a furnace for a gas water heater exhaust. (High temperature).

Anyway, I taped up all the cracks and holes and then the puppy worked fantastic!

As stated above, it's possible your cold air is being recirculated in over and over and over again, never allowing warmer air over the coils, thus causing the freezing.

I agree, check inside and make sure you have good separation between intake and output sides. Some tape goes a long way.

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