Coleman mach 3 ac freezing up

Could be low on refrigerant or not enough air flow across the coil.

The 'freeze probe' has to be inserted into the fins of evap coil...lower section

Old-Biscuit wrote:
The 'freeze probe' has to be inserted into the fins of evap coil...lower section

He said COPPER tip sensor. He does NOT have a wall tstat unit. He has ceiling mount controls and that copper tip is the tstat sensor only.
To the OP, NO, that copper tip is NOT supposed to be in the evap fins. It is supposed to be in the air flow where it is right now. You need it checked by a pro. Doug

Remove the "new" filter for a day or 2 and see if additional airflow solves....

Very possible the Ceiling tstat is bad. If on HI COOL, RV roof top units with mechanical controls rarely freeze up due to the higher volume of air over the coils. They usually freeze up on the lo fan speed. Which is normal. Doug

wwest wrote:
Remove the "new" filter for a day or 2 and see if additional airflow solves....

Try this. Also check that you put the filter in correctly, and that the evaporator is not clogged with dust or dirt.

If that's not it, you are low on refrigerant, which makes the compressor run continually & therefore you get icing. You likely are not hearing the compressor cycle because it's running all the time.

You will also get freeze up running with low outdoor temperatures- if the condenser coils are in the low 70's, the evaporator coils will be below freezing.

Thanks for the help. We did run it without the filter and it still froze up. The t stat is part of the roof unit and not on the wall. What type of freon is in this unit? R22 like a house? I talked to my local rv shop today and they dont work on ac units, only replace the whole system. If its the same freon as in a house maybe I can get my ac guy to look at the camper ac.

SC camper wrote:
Thanks for the help. We did run it without the filter and it still froze up. The t stat is part of the roof unit and not on the wall. What type of freon is in this unit? R22 like a house? I talked to my local rv shop today and they dont work on ac units, only replace the whole system. If its the same freon as in a house maybe I can get my ac guy to look at the camper ac.

1. IF it is low on Freon/410a, then it has a leak and will lose all its coolant and not cool or freeze. So, you do not have low coolant. They only hold 16 ozs of coolant.
2. Yes, they do NOT (we also) work on the sealed system or coolant as it will cost you more than the upper unit is worth. Regular Home AC people have no clue on how to fix or charge RV AC units.
3. You need it checked out by a Qualified RV AC Technician
4. I believe you have a BAD tstat as I stated previously. Turn the Tstat knob back and forth. You should hear a click as the contac points open and close. DO NOT hear the click, then the tstat is stuck ON causing your freeze up. Doug

It's going to be charged with R22 or R410a. The newer units use R410A. The unit can be checked(by a knowledgeable tech) for correct charge by using a clamp on meter. Using a piercing valve to attach gauges is irrelevent because that leaves a hole that must be repaired, a service port brazed in and the unit recharged anyway. Everyone likes to jump on "low freon" as the usual cause but these units only hold a pound of refrigerant and if you get a leak, you will almost always lose the entire charge.
R22 is relatively easy to charge, even by pressures. R410a, not so because it runs at such high pressures and is pretty unstable and has to be charged by weight or by superheat. Most RV shop techs will not know how to do that or will not have the equipment and that's why they always try to sell a new unit.