Quote:
Originally Posted by Austinformedude
I checked the gas, and pressures. Everything was fine. I found that by leaving the fan speed low AND the temp low (75 or lower) the evaporator will freeze up in about 5 hours with outside temps over 90F. I don't normally take trips that long though. I think what is happening is with the low air flow, the icing isn't getting knocked off the evaporator. Now I just run the fan speeds higher and no more problems.
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It's not the heat, it's the humidity. With an adequate combination of heat and humidity any AC will freeze up. Keeping the fan speed low makes it worse, as the compressor will never cycle off. Using the Max AC setting helps, because that recirculates air from inside the cabin that's already been cooled and de-humidified, instead of pulling in more hot and humid air from the outside.
I once worked at a motel that had inadequately sized window AC units. On an average day no problems, but when above 90 with high humidity they would build up literally a full inch of ice on the coils. The users in these cases always had the temp control set all the way down, which made the situation worse, as the compressor never shut down. The temporary fix was to simply turn the temperature up. The compressor would turn off, and the ice would melt. Since they did not have the ability to recirculate the air in the room there was no permanent cure except to replace them with higher capacity units that didn't have the compressors running at a 100% duty cycle to cool the room.