AC unit freezing up

[Jkoht]

It got hot here in MN this weekend, and the humidity went up and down as well. While staying in my parents camper, a 2008 Salem, the AC unit seemed to freeze up at one point. The unit is controlled by the ceiling panel. At the time the fan speed was on the low setting, and the temp knob was set on the coldest. The air started blowing even slower than the normal low setting, and the cold air didn't seem to be coming out. I turned the fan to high and dropped the temp knob to the 3/4 position. After a while ice melted and broke up and actually came out of the vents and the fan speed went up to normal. Is it possible that during times of high humidity that unless you have the fan running on high it can freeze like this? Is there something I can do to ensure this doesn't happen again?

 

[donn]

Quite common actually. Had it happen all the time when I was running both ACs in my fiver. The solution is set the temp to warmer and rur the fan speed up.

 

[docj]

The solution is set the temp to warmer and rur the fan speed up.

Right, our new Coleman Mach8+ are prone to freezing unless you run them on high. Even on high they're less noisy than the Dometics they replaced.

 

[Mr Lars]

Happens a lot, we usually have that happen during the night. We just move the control off a/c to fan only, within a few minutes the frost and ice melts off the exchanger, airflow returns to normal, then we move the switch back to a/c.

 

[Firefighter1406]

Has the same thing to me a couple years ago. Talked to an old timer and he said in the summer if you try and run them on anything other then high they will ice up. I was running it on low at the time. Cranked it up and two campers later no problems. We are currently camping in the high 80’s and A/C has been good the whole time.

 

[RFSims]

Got a buddy who is a retired HVAC teck. He told me the number one problem to cause a freeze up is the unit is low on freon. Being the unit is 13 years old might want to have the freon checked. Adding freon has always solved my AC freeze ups.

 

[Rene T]

There are no charging ports on a rv AC.

 

[Mark_K5LXP]

I guess not all A/C units have freeze thermostats on the evaporators? I wouldn't think it'd be hard to add one.

Mark B.
Albuquerque, NM

 

[Henry J Fate]

I guess not all A/C units have freeze thermostats on the evaporators? I wouldn't think it'd be hard to add one.

Mark B.
Albuquerque, NM

I think the units the OP is referencing do have freeze stats (thermister) from the factory.

Check the specific service manual for the unit in question post the make and model number and a member will certainly respond.

The freeze stats (thermisters) will change characteristics over time and willnot send the required signal which cycles the compressor off prior to freezing. Replacement becomes necessary. Locating the freeze stat is easily done. It can be found in the evaporator coil with a couple of wires to it.

In the case that the unit does not have one from the factory, adding one is a good idea and can be wired into the compressor control circuit (usually 12 volts) which will cycle the compressor while you sleep or any other time a freeze is imminent.

Low refrigerant is a possible cause. If the unit is low on refrigerant, finding and fixing the leak and adding refrigerant is usually not a sensible or economical option unless you have the skills, equipment and tools to do it yourself.
Replacement of the unit is the most likely option.

 

[John From Detroit]

There are several reasons for an A/C to freeze up. First thing is to insure the air paths, both indoors and out, are clear (Usually the condenser (Rooftop) is crudded up and other than on coleman's it's on the 'inside" Coleman's it outside where it is way easier to clean)

Next is turn the fan to HIGH

 

[John From Detroit]

There are several reasons for an A/C to freeze up. First thing is to insure the air paths, both indoors and out, are clear (Usually the condenser (Rooftop) is crudded up and other than on coleman's it's on the 'inside" Coleman's it outside where it is way easier to clean)

Next is turn the fan to HIGH not low, Not auto, but HIGH
I know it's noisy but you'd be amazed at how fast you learn to "Tune it out" and the noise blocks the knock down drag out fight 2 sites over from bothering your sleep.

 

[docj]

Has the same thing to me a couple years ago. Talked to an old timer and he said in the summer if you try and run them on anything other then high they will ice up. I was running it on low at the time. Cranked it up and two campers later no problems. We are currently camping in the high 80’s and A/C has been good the whole time.

The technician who installed our Mach8+ heat pumps said the same things. I commented that with the heat pump in use there is ONLY a high fan speed and his comment was that "you shouldn't be using the low speed for A/C anyway!"