So the past few nights, my A/C unit mounted on the roof in my camper trailer keeps freezing up and can't figure out why. In the same campground I've been in for weeks with no problems. This started right out of the blue. Still works great and runs on high all day with no issues pumping out cold air. Works til about 3 AM and the inlet or whatever freezes over solid with no airflow. No drastic changes in the weather either. Can't lock on to anything different I could be doing inside the trailer to cause this. Any ideas or help?? Thanks guys.

 

turn it off your camping........... but i digrest, simply turning it down at night will help out, or the coils need cleaning.

 

But in the mean time, when you go to bed, leave the thermostat at it's usual setting but leave the fan run continuously until you can get the unit cleaned.

 

Restriction due to a dirty or clogged intake filter can cause icing where none existed before.

Basically, the unit has to work harder to suck in the same amount of air. Icing can result.

If the intake vent and filter is undersized the problem is more likely, IMO. If you want to test it, remove any filter in the intake and see if it still freezes up. If not, replace the filter with a new one.

 

If your filter is not stopped up, or if it don't have a filter, and your evaporator coil is clean. More than likely, your system is low of freon. A low freon condition will let the pressure inside the freon system drop in low ambient temperature conditions. During the daytime, the ambient temperature is high, thus causing the internal pressure to increase to a condition that allows it to work properly. I know that sounds crazy, but it is true. When the pressure is too low, it allows the gas to expand to more, and create a sub freezing temperature inside the coil. Then the moisture sticks to it and freezes.
I know this is accurate, because I have walk in coolers that have the problem in extreme temperature fluctuations. it seems in the hottest part of the summer I have to lower the freon level, because it becomes over pressurized. Then in the Winter, freon has to be put back in the systems because it contracts due to the low ambient temperature. It is a delicate balance, because of Freon's characteristics.

 

Tumba's spot on here. So are the ones talking about restrcted air flow. I've had similar problems with my home AC. The filter box is too small so I have to clean the filter almost weekly to avoid freezeups. Low freon will also cause the problem (had it happen). A combination of the two makes it just that much worse.

What you can do for yourself is to make sure the filter and coils are clean and the ductwork is clear of obstructions. Run the registers as wide open as possible. If the doesn't help, you probably need freon added. if it happens again, then you need to also check for leaks.