dometic ac shutting down at night

[jimack]

my dometic a/c runs fine during the day but shuts down at night. i can get it going again by turning the thermostat off then back on. it will run for several minutes then shut down again. i've noticed that when it does the compressor and fan shut down at the same time. i'm thinking that when it is working right, the compressor shuts down then the fan a few seconds later.
the control board has been replaced and the thermostat inside replaced.
problem seemed to disappear for a couple months but returned.

i have read other post about the same problem with their dometic a/c but have not read of a solution.

at present, it gets into the 60's here at night but the inside temp is above 70.

[time2roll]

Also check the lower section plenum divider is properly placed and sealed or a percentage of the air can circulate within the system instead of cooling the RV.

[fixpro256]

jimack, Did you get your problem fixed? Mine does the same thing. Folks keep trying to address the freezing issue. That isn't my problem. My problem is that the fan doesn't do what it is supposed to do when it does "freeze"(actually just getting the coils too cold).

Dometic says the fan is supposed too go to high when the unit "freezes". Mine doesn't. Unit shuts off compressor and fan at the same time. Thermostat will be set on 76 but the room will be much warmer. Can get it going again by setting fan to a different mode or going to "off" then back to "cool".

I was about to order a circuit board/thermostat kit, but I see some post where people have replaced the board and thermostat and still had the problem.

[agesilaus]

Read my post. IF you have a wall tstat, and your unit freezes, you have a operational problem that needs fixed. The Internet is NOT always the best place to get correct Info. Doug
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I won't argue with that. I already cleaned the inside filters but I'll get on the roof and check that one and the coils.

[dougrainer]

jimack wrote:
my dometic a/c runs fine during the day but shuts down at night. i can get it going again by turning the thermostat off then back on. it will run for several minutes then shut down again. i've noticed that when it does the compressor and fan shut down at the same time. i'm thinking that when it is working right, the compressor shuts down then the fan a few seconds later.
the control board has been replaced and the thermostat inside replaced.
problem seemed to disappear for a couple months but returned.

i have read other post about the same problem with their dometic a/c but have not read of a solution.

at present, it gets into the 60's here at night but the inside temp is above 70.

One thing you need to check. Do you have a cold air vent blowing on the wall tstat? That would cause shut down especially at night. Also, the separator plate between the Air Intake and the cold air exhaust needs to be checked and make sure there is no bleed over. THAT also would be a factor at night. Doug

[dougrainer]

agesilaus wrote:
Well my unit ices as I mention above and it does it at night most of the time. Checking on the net brought up the icing issue and said that this is frequently blamed on other issues. So try running the fan, it's cost free and is minimal hassle. Maybe it's something else but eliminate the simple first.

Read my post. IF you have a wall tstat, and your unit freezes, you have a operational problem that needs fixed. The Internet is NOT always the best place to get correct Info. Doug

[dougrainer]

DFord wrote:
The indoor coil is protected by a "freezestat" to keep it from frosting/icing over and stopping all the passage of air from the blower. When you turn the a/c off and back on that safety feature is reset until the next time it frosts up. Running the fan on continuously allows the frost to melt when the thermostat cycles the compressor. Make sure the air filter and the face of the indoor coil is clean. The coil has a habit of matting over when dirt and dust get past the cheap filters used in RVs. You'll need to take the plastic cover off the inside and look up there with a flashlight to see the face of the indoor coil.

1. The freeze Thermister is not a safety item
2. Once the Freeze Thermister trips from freezing, the ONLY thing that resets it is for the Coil to warm up. Turning the power OFF or resetting the Tstat will not bypass a Freeze Thermister that has tripped from freezing.
3. Running the Fan continuously(on HI) just keeps the Evap coil from freezing. If you run it on LO cool or AUTO, it may freeze. On Auto, the fan runs on HI then goes to LO as it nears the preset temp and THAT fan speed change can cause a freeze up if the Freeze Thermister is inoperative.
4. IF you have a wall tstat, the Evap CANNOT freeze regardless of Fan setting or on Auto. Wall Tstat AC systems have the Freeze Thermister. So, IF your unit freezes up, either the Freeze Thermister is defective(very rare) or the Thermister is not installed in the evap or in the wrong place in the Evap. Doug

[DFord]

The indoor coil is protected by a "freezestat" to keep it from frosting/icing over and stopping all the passage of air from the blower. When you turn the a/c off and back on that safety feature is reset until the next time it frosts up. Running the fan on continuously allows the frost to melt when the thermostat cycles the compressor. Make sure the air filter and the face of the indoor coil is clean. The coil has a habit of matting over when dirt and dust get past the cheap filters used in RVs. You'll need to take the plastic cover off the inside and look up there with a flashlight to see the face of the indoor coil.

[agesilaus]

Well my unit ices as I mention above and it does it at night most of the time. Checking on the net brought up the icing issue and said that this is frequently blamed on other issues. So try running the fan, it's cost free and is minimal hassle. Maybe it's something else but eliminate the simple first.

[time2roll]

I was going to say probably the thermostat but seems odd as it was just replaced. Still might be as it seems dometic has some with issues. May as well post what thermostat you have.

Otherwise I would set the thermostat higher at maybe 78 during the day and see if it will cycle normal.

Would not hurt to check the freeze sensor is placed properly in the evaporator. Or to check for ice right away when it shuts down.

[agesilaus]

First guess is icing, switch from a/c to fan for 30-60 min and that should melt the ice.