Coleman AC freezing up constantly?

remove roof shroud clean drain pan and hose, make sure drain is open, blow dust out of Everything
run fan on high..
with shroud off run A/C make sure condensation is running out of drain pan onto roof
if its not draining, it fills up, blower will pick it up and the moisture freezes on the coils
run a/c fan on high you Must move Lots of air to keep coils dry

I believe that all RV air conditioner manufacturers recommend running on high fan in humid conditions to prevent freeze up. I know it is right in the operating instructions for my Dometic.

If the roof A/C is icing then
1: Clean intake filters inside the RV

2: Clean evaporator coils if needed (NOTE: you have to go topside to do this but you can inspect them from below while cleaning filters)

3: Clean CONDENSER coils.. (Might as well).

4: Run fan on HIGH

5: Check for the frost sensor.. this is a probe that on SOME models is stuck into the evaporator coils, near the bottom.. I have read of cases where it was lying in the drip tray and absolutly not working.. NOTE: NOT ALL A/C's have this,, But if yours does, it should be stuck in the evaporator coils.

Side note: One of my Carrier units was tripping its 20 amp breaker.. I went topside yesterday and cleaned the condenser. So far, the breaker has held.

If it's a Ducted A/C, using a Wall Thermostat, it has a Freeze Sensor that has to be correctly placed on the Evaporator Coil. That's the one you can't see till you pull the shroud and the front of the sheet metal cabinetry. If it's Ducted, be sure the Ducting is properly connected and hasn't shifted so as to form an obstruction to air flow.
If it's NOT ducted, NO freeze sensor. If you clean it (and be sure to clear the Drain Pan Holes!) you may be able to get by with running it on LOW. It's pretty humid in FL and we can run our Coleman Mach 15 non-ducted on Low. Otherwise, HIGH fan speed really helps.
The pix above probably came from Chris Bryant's Article and reading that should help you get the job done.

Thanks for your replies, so helpful! ddndoug--yes mostly on low, but occasionally on high.

Are you running it on low fan speed?

Doug

Up on the roof top you must go :B

Remove shroud.........then remove sealed cover over evap coil.

Opening below evap coil is where your filter covers so place a towel etc. over opening so you don't get anything down inside Rv when cleaning evap coil.
After it is clean.make sure evap coil drip pan drain holes are clear/free flowing
Reinstall evap coil cover and seal it back up.
Clean the condenser coil and fan blades.
Reinstall shroud

Now get back down off roof.

Have you cleaned the evaporator coils? If they are dirty you will not get enough air through them and can/will ice up. Most of these units are sealed systems and freon cannot be added. Pull both outside and inside covers off. On roof you should be able to remove shroud covering evaporator fan and coils. I used my air compressor and back blow air through the coils, mind you this will also blow all the******back into RV. Once that is done I spray coil cleaner on both sides of coils, let sit and use a pump sprayer to rinse coils. Make sure you have towels on the floor. Not hard to do just messy. Clean out your condenser coils before closing everything back up. Hope this works. Good luck.