AC Freeze Lockout

[suny07]

Hi,

we are currently in South Carolina and our AC is having an error during night.
It states "AC Freeze Lockout".
We had this now 2 nights in a row.
We also stayed here the last 3 years with our Monty and never had this issue.

The AC is set to 68F or 67F, outside at night app 73-78F.
Humidity around 70-80%.

I think our AC is dometic blizzard nxt 15k with heat pump.

Any suggestions what I can do to fix it?

Thanks,
Mike

[DutchmenSport]

Don't know if this is what is happening to yours, but sometimes when air flow gets restricted across the cooling vents (on the roof), the cooling fins and/or cooling unit will begin to ice up. Without air flow, the condensation that forms will begin to turn to ice, instead of evaporating, or running off. Once ice begins to form, the air flow is even more restricted, until after a very short while, an ice dam forms on your cooling fins, around the compressor, and cooling unit.

The simple solution is to simply turn off the air conditioner and let everything completely melt away.

The air conditioner needs to cycle on and off systematically, especially in very humid conditions, so during "off" part of the cycle, the ice that may form has a chance to melt away and turn back into water and drain away.

After your ice has melted away (give it a good couple hours at least), turn the AC back on. But if the outside temperature is 78, turn the thermostat to 76. Let it cool until the AC turns off because the inside temperature reached 76. Wait a few minutes and then lower it a couple more degrees. Let it run until it reaches the new temperature and wait again. After some time, lower the temperature again, until you finally reach your desired temperature. This slower process allows the ice to melt, which is a problem when the humidity is very high. If you simply turn the AC on and let it run and run and run without cycling on and off, in high humidity times, they do ice up.

I certainly hope this is all you have to do.

FYI, we have our cooling unit(s) - 2 of them - in the attic of our house. I have, in the past, seen ice form so think of those coils and fins, it had to be 2 or 3 inches thick. In 15 years of living in this house, I've seen them do this about 3 times.

In a previous camper, I had this problem too. I'd remove the return filter and could look up and see the inside of the AC, and it was covered with white ice up there. That's when I learned to lower the temperature slow. Ever since then, we've never had a problem icing up again. Meanwhile, in the house, last year we got an whole new AC unit on the one end of the house. I'm curious if it will ice up sometimes too.

Another thing to check, is to get on the roof of your camper, remove the cover from the AC, and make sure the fins on coils unit are not obstructed with dirt, bugs, leaves, and junk causing air flow restriction. If so, a simple hand brush, stroking with the fins, so you don't bend them, will clean them out pretty good. Otherwise, use a garden hose and spray them out.

[TWP723]

Running the temps too low will cause the compressor not to cycle on and off and freeze up the system. Also if the fan is running on low on a very low temp setting. Bad thermistor.. Possibilities.

[DQDick]

With that temp and humitity we would run the fan on high and possibly raise the temp setting to keep the coils from freezing.

[rohrmann]

Many A/C units have a freeze sensor that has a probe inserted in the fins that senses when ice forms and shuts of the compressor until it warms, then allows the compressor to start up again. If this probe has fallen out it can’t work. Maybe this could be the issue?

[suny07]

Thank You.

We try to cool it down slowly tonight.

[RMcNeal]

I think Bob is onto something. Take off the shroud on the top and look to see if the freeze sensor is still in place. Also removing the shroud will let the ice clear up faster. While your at it, make sure the small tracks and weep holes are not blocked in the bottom half of the shroud so that any condensation can run out. You may need to clean the coils while you're at it. I use this...https://www.amazon.com/dp/B00DM8KQ3I...v_ov_lig_dp_it. I does a pretty good job and you don't have to wash it off. I usually use a spray bottle of water to rinse lightly. Make sure none of your fins are smashed or block as well. Here's a good video on maintaining your AC.

https://www.youtube.com/watch?v=Gbm8hOyZlrU

[suny07]

Hi

Cooling down in slower increment steps helped us on the issue.

I opened the AC and there is no debris or any blockage inside.
The probe I could not locate and let my dealer check on it the next time.

Thank You
Mike

[Butch & Kathy]

I just replaced my Blizzard after trying all of the above, even bought a new freeze sensor. It is worth while removing the shroud and the styrofoam interior compartment to access the freeze sensor to make certain that it is installed and has not fallen out of the fins. The good news is that $1500 later (AC + install) my AC is working great and I don’t have to fool with the touchy temperature adjustments...