Hi all,
I'm not an A/C expert (but I did spend the night at a Holiday Inn Express)
Usually, an A/C unit will ice up on the evaporator due to insuffecient airflow (ie: dirty filter or dirty evaporator coil. This prevents the freon from removing heat, and thereby the coil just keeps getting colder. ( An A/C evaporator coil will normally run at 40 deg F.)
If the coil iced up at nite, it was probrably due to the outside air temp decreasing to the point that with the unit set on the lowest temp setting the freon was staying in the outside condenser, and whatever freon was reaching the evaporator was boiling off much too fast, thereby lowering the evaporator coil temp to 32 deg F or below.
The temperature control on a window unit is different than the thermostat in a home central air unit. It is a capillary tube filled with freon that reacts to the temp across the evaporator coil, rather than a coil spring (or digital thermocouple) that is in a home central unit. It might be that when the TM unit is set to max it will never shut off. I would recommend backing off just a little, to allow the unit to cycle on & off.
Another reason an A/C might freeze up is a low freon charge. A car system has a low pressure cut-off switch to prevent damage to the compressor if you have a low charge, but a window or home unit does not normally have this protection. Unless the window unit (IE: TM) has a service valve, it is sealed & you don't usually lose freon unless you have a catastrophic failure (ie: compressor electrical connection failure or punctured condenser or evaporator coil or copper tubing line or solder joint).
Maybe we should start another thread, as this is not even remotely related to water heaters.
As an aside, if you are having problems cooling your TM with a side mounted A/C, check to see if the intake & exhaust air for the condenser are separated & not mixing together. Especially if you have replaced the original unit. I saw one at the Jubilee which was replaced with a unit that was not as deep as the original, & did not extend all the way to the outside grill. The air is pulled in on the sides & exhausts out thru the condenser coil. I recommended the owner place some kind of cowling around the condenser which extended to the grill (which he did & the unit was cooling better). This helps to prevent the hot air from the condenser coil being recirculated back across the coil.
Have a great day & stay cool.
Dan