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Old 10-19-2020, 07:56 AM   #1
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AC Freezes Up

I have a ducted Dometic AC in my 5th wheel. When having the air vent opened to just the main area the AC works great. When I change the vent to force the air through the ducts the AC freezes up with very little airflow to cool the trailer.

Is this a design flaw of the Dometic unit or do I need to replace my AC?

Anyone else experience this problem?
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Old 10-19-2020, 08:22 AM   #2
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it is more then likely freezing up due to poor air flow clean the filter and check the ducts for obstructions. Make sure all the ac duct covers are open
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Old 10-19-2020, 08:36 AM   #3
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Quote:
Originally Posted by dangerruss View Post
I have a ducted Dometic AC in my 5th wheel. When having the air vent opened to just the main area the AC works great. When I change the vent to force the air through the ducts the AC freezes up with very little airflow to cool the trailer.

Is this a design flaw of the Dometic unit or do I need to replace my AC?

Anyone else experience this problem?

We were having the same issue on a new 2019 FXS 260RT.
Mine is ONLY ducted...do not have the 'dump' feature....and no thermostat...just the dials on the unit.

Read a post on here about folks thinking the A/C worked like the one in your home...not, its only going to cool down so much from ambient temp...and another post about the divider between the return and discharge air paths.

I found the divider between the return air and discharge air was not in place properly...was cocked allowing the air flows to mix...fixed and sealed that and still would freeze up.

We found that...after the unit cooled down to a comfortable temp if I would turn up (warmer) the temp dial till the compressor would cycle off and it would continue to maintain that temp...and cycle without freezing up.

This method has proven functional for us in the Texas summer heat and in the mountains of Colorado.
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Old 10-19-2020, 08:47 AM   #4
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AC freezing up

I have a 260 FXS Wildwood but a friend has a Salem and had the same issue. There is a piece of ductwork that has fallen and is blocking your airflow. If you pull the cover off at the filter area and look up in the air return you will be able to see it. We just used duct tape to keep it in place and not block the flow.
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Old 10-19-2020, 11:31 AM   #5
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Originally Posted by SeaDog View Post
it is more then likely freezing up due to poor air flow clean the filter and check the ducts for obstructions. Make sure all the ac duct covers are open
It is definitely due to poor air flow. Filter is clean and all AC duct covers are open. Going to check for obstructions when I return to CO next spring.
Thanks..
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Old 10-19-2020, 01:29 PM   #6
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Quote:
Originally Posted by Moore Travels View Post
We were having the same issue on a new 2019 FXS 260RT.
Mine is ONLY ducted...do not have the 'dump' feature....and no thermostat...just the dials on the unit.
Are you sure it's DUCTED a/c? Ducted a/c uses a wall thermostat that also controls the furnace.
It sounds like you have a BFC(Blast From the Center)NON-ducted a/c unit.
DUCTED a/c has adjustable ceiling vents throughout the RV.
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Old 10-19-2020, 01:48 PM   #7
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On-line photos of the interior of this trailer sure look line non-ducted AC in the ceiling.

The non-ducted AC in my popup had the controls on the ceiling with just vague numbers on the dial. This unit would occasionally freeze up in very humid conditions if the fan was run at low speed. On High it was fine.

The ducted AC in my Roo has 8 cold air outlets in the ceiling (there are ducts in the ceiling), no controls on the unit, and temperature and fan controlled by the wall thermostat just like at home.

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Old 10-19-2020, 02:05 PM   #8
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Quote:
Originally Posted by bikendan View Post
Are you sure it's DUCTED a/c? Ducted a/c uses a wall thermostat that also controls the furnace.
It sounds like you have a BFC(Blast From the Center)NON-ducted a/c unit.
DUCTED a/c has adjustable ceiling vents throughout the RV.


Yup...ducted...controls on filter/return grill...A/C only in celling ducts with ceiling vents throughout...they swivel, but are not adjustable as far as flow.
Thermostat on wall for anemic propane furnace....which we never use...the electric fireplace does the job!
Wish it had a 'dump' BFC selector...would make it cool off faster when we first fire it up!
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Old 10-19-2020, 02:09 PM   #9
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Quote:
Originally Posted by Moore Travels View Post
We were having the same issue on a new 2019 FXS 260RT.
Mine is ONLY ducted...do not have the 'dump' feature....and no thermostat...just the dials on the unit.

Read a post on here about folks thinking the A/C worked like the one in your home...not, its only going to cool down so much from ambient temp...and another post about the divider between the return and discharge air paths.

I found the divider between the return air and discharge air was not in place properly...was cocked allowing the air flows to mix...fixed and sealed that and still would freeze up.

We found that...after the unit cooled down to a comfortable temp if I would turn up (warmer) the temp dial till the compressor would cycle off and it would continue to maintain that temp...and cycle without freezing up.

This method has proven functional for us in the Texas summer heat and in the mountains of Colorado.
PS - I omitted an important fact about this method...always leave the fan speed on High...soon as I turn it to Low...it freezes up again...we just use the Temp adjustment to adjust the comfort level.
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Old 10-20-2020, 08:46 AM   #10
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Quote:
Originally Posted by bikendan View Post
Are you sure it's DUCTED a/c? Ducted a/c uses a wall thermostat that also controls the furnace.
It sounds like you have a BFC(Blast From the Center)NON-ducted a/c unit.
DUCTED a/c has adjustable ceiling vents throughout the RV.
Yes. It is ducted and I have a wall thermostat that controls cooling and heating.
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Old 10-20-2020, 08:57 AM   #11
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Quote:
Originally Posted by Chuck_S View Post
On-line photos of the interior of this trailer sure look line non-ducted AC in the ceiling.

The non-ducted AC in my popup had the controls on the ceiling with just vague numbers on the dial. This unit would occasionally freeze up in very humid conditions if the fan was run at low speed. On High it was fine.

The ducted AC in my Roo has 8 cold air outlets in the ceiling (there are ducts in the ceiling), no controls on the unit, and temperature and fan controlled by the wall thermostat just like at home.

-- Chuck
Not sure what online photos you are looking at...
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Old 10-20-2020, 09:01 AM   #12
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Originally Posted by dangerruss View Post
Yes. It is ducted and I have a wall thermostat that controls cooling and heating.
Check and make sure the freeze sensor has not fallen out of the evap coils
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