Dometic AC freezing up

[H2oclass1]

My Dometic AC keeps freezing up. The freeze sensor reads 74° all the time, so I replaced the sensor. The new sensor never goes below 73°. I don’t think it would be low on freon or the freeze sensor would indicate that. Any ideas on what I should do next?

[dougrainer]

H2oclass1 wrote:
Doug
I have seen the coils ice over.
I swapped the stats and the problem did not follow.
I only have the problem on 1 unit the other 1 is working fine.
Kenny

You need to contac the Tstat maker. I have NEVER---NEVER had a AC control board malfunction for a freeze sensor. It is ALWAYS the freeze sensor malfunction. Try swapping the good sensor from the other AC unit.
Is your control board in a 6 by 6 galvanized box? If so, I would swap the control units. Very easy to swap. Since I never work on systems that have modified parts(your after market tstat system), you really need to contac Easy air. With Dometic Control and tstat, I have NEVER had a problem like yours. The aftermarket tstat system makes troubleshooting much harder. Doug

[dougrainer]

prichardson wrote:
If you are getting icing you likely have an an airflow problem. Is evap. coil clean? Filter clean? Duct work clear and ALL registers open? Ceiling assembly installed and sealed correctly?

IF you have a functioning freeze sensor system, you WILL NEVER get ice regardless of conditions. Doug

[prichardson]

If you are getting icing you likely have an an airflow problem. Is evap. coil clean? Filter clean? Duct work clear and ALL registers open? Ceiling assembly installed and sealed correctly?

[H2oclass1]

Doug
I have seen the coils ice over.
I swapped the stats and the problem did not follow.
I only have the problem on 1 unit the other 1 is working fine.
Kenny

[dougrainer]

1. That tstat is NOT a Dometic wall tstat. That is an aftermarket tstat.
2. You need to contac the Easy touch people for help. The freeze thermister WILL READ the evap and it will get below 60 degrees.
3. The AC only holds about 1 lb of coolant. So, if a leak, it will leak enough to NOT freeze or even cool.
4. Remove the sensor from the evap. Unplug one wire from the control board. IF the compressor comes ON, leave it that way. If not, jump the 2 wires together and leave and observe operation.
5. Have you actually seen the coils covered in ICE? Doug

PS, SWAP the wall stats and see if the problem follows.
Do BOTH AC units do this?

[H2oclass1]

Evaporator. My bad.
2015 Forest River Georgetown XL
AC Model B57915.711J0 with a EasyTouch RV thermostat
On the thermostat info screen, it shows the temp.
Some info I found in the manual:
Freeze Fault: Temperature of inside coil has dropped below 30°F (-1°C). The compressor will turn off and the fan will run until the inside coil sensor temperature reaches 54°F (12°C). The compressor will then run again if required. This fault can mean the air flow is restricted, filter is clogged, outside coils are dirty, refrigerant is low, humidity is very high, or the sensor is bad if becomes a recurring problem. • Freeze sensor: The control board will report three errors for the freeze sensor. BR = bad reading (out of range), OP = open sensor, MS = missing sensor. These letters will show in the freeze sensor temperature location in place of the temperature.
I am getting no errors.
To make it even more interesting. I have 2 AC’s, this morning with both off the temp is the same 63°. I’m still leaning towards replacing the circuit board but not sure.

[30sweeds]

Compressor relay probably sticking or stuck due to the bad freeze sensor.

[dougrainer]

1. There is NO freeze sensor in the condenser.
2. The Freeze sensor is mounted in the evaporator coil.
3. What Year Brand Model RV?
4. What Model AC and what TYPE wall tstat?
5. HOW are you reading the Freeze Thermister temp? Doug

[time2roll]

I agree the control box is malfunctioning if the freeze sensor is buried in ice is interpreted as 74/73F.

[Blacklane]

There are some trouble-shooting manuals on-line that may help you.

I assume the freeze sensor goes to a control board that controls the compressor, etc. The next step is probably to trouble-shoot or replace the control board.

[H2oclass1]

In the same place I took out the old one, in the condenser.
Or in this case in the ice. 🙂

[wa8yxm]

Where is the freeze sensor located?