AC unit freezing up.

The most likely problems with these and most other ACs, including window bangers, is dirt. All my RVs have had Dometic and all the service calls I've had for RVs out in the BF desert have been for Dometics. You have to take off every cover that will come off (even if it's not meant to be a consumer serviceable item) and clean the coils AND the cond fan blade and evap blower wheel TROROUGHLY. The cond coil plugs up on the inside where the average bear never looks and the slightest amount of dust in a forward curve blower wheel kills them, plus the dirt you can't see in the evap coil. I've had my own ACs plug the condenser in one year! I blow mine out every year and do a thorough soap/water cleaning every two years. The mfgrs engineering data on an AC shows how much the sensible and latent loads are brought down and it has to do with coil sizing, airflow and ultimately the DTs. Dometics are major over achievers on the evap DT so they are strong on the latent load and dehumidifying. I ALWAYS run mine on hi to keep head pressure as low as possible and help the already low airflow problem across the evap. Square heel/square throat 90s are terrible for restriction (square throat/radius heel 90s aren't any better) and RV ducted systems have nothing but square bends in the airstream. Turning vanes cut the resistance of a square 90 in half but RV mfgrs don't use them anywhere. Even opening the quick-cool diffuser on these Dometics doesn't get the evap DT down to the normal 20, so it's obvious they aren't designed for the right cfm/ton of cooling - 350 - 450, depending on if designed to bring down the latent or the sensible loads more. I'm so anal about air restriction, I cut down the huge elec. box that Dometic puts right smack in the middle of the return air so it doesn't block the air flow. I just did a thorough cleaning on my Dometic 15k and evap DT is 29 (just like every other Dometic I've had) cond DT is 25 (not bad but lower would be nice) discharge line temp 182 (good) and suction line temp is 40. No freezing at that suction temp but EER (energy efficiency ratio) sucks with that high evap DT. There are many factor for high EER and it comes partially from lower evap DT, which works on the sensible load more than the latent load. Our RV ACs aren't too efficient and they work on the latent load, big time, but that's not all bad cuz lowering the RH is a big comfort booster for most people. As far as the freeze stat in these ACs go... they wouldn't need to be there if it weren't so likely to run the evap so cold because of their poor engineering (high evap DT and/or low suction temp), plain and simple. Sooo... clean, clean' clean and run on high! TXiceman and I went to different schools together! I also started this trade in 70. Craig