ralexis
Flagstaff, AZ
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Joined: 12/09/2003
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A/C froze up last night. Dometic 13,500 rooftop. We were in the AZ desert and temps were 100 +. I shut down the compressor and left the fan running and the ice melted quickly. No more problems yet. What causes this to happen? Any preventative maintenance suggestions?
Not fun to have no A/C in the desert.
Thanks
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thomasinnv
where ever i stop
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not much you can do. when they work that hard in those high heats, the compressor does not get a chance to cycle off and on, so the condensation does not have a chance to melt off the coil. just the nature of the beast.
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Rollincool
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No humidity in the air and not enough air passing the coils is what causes freeze ups.
When you turn up the thermostat, or should I say turn down, just move it slowly until the unit JUST comes on. That should help. And don't run on slow fan speed.
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janstey
Glenwood, IA
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Clean your filter often also.
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Mandalay Parr
Phoenix, AZ
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Run the fan on High and make sure the filter is clean.
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javaseuf
Southern Cal
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In a properly maintained and operating RV roof air, freeze-up should not be a problem whether on high or low fan.
Other than low refrigerant, if there is sufficient air-flow over the evaporator coil, freezing will not occur.
Things that will reduce proper air-flow are:
Dirty filters
Dirty evaporator coil
Defective blower motor
Bad seal between the supply and return air plenumns
Another cause of freeze-up is the defrost sensor falling off of the evaporator coil. Mine did this when it was new. This sensor is only on ducted systems.
We have had many days in my area with 100+ degree weather and my 15k Dometic runs just fine with no freezing. In fact, when it getts a little too cold, I usually run the fan on low. This forces the compressor to run longer and yesterday, my compressor didn't shut off for 6 hours. No freezing problem.
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tom1984
Olive Branch,Ms
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My Dometic 15,000 has always frozen up since new if the outside temps were not above 90. This thing cools great so I have never wanted to mess with it. If the outside temps are not hot enough I just turn the thermostat up a notch and it works fine.
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BillyP
Cedar Point, NC
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A couple things can cause freezing up of the coils -
1 - poor air flow across the coils. Too many outlets closed (if a ducted unit) or only opening one end, of the discharge on a non-ducted unit. Dirty filter. Something in the duct blocking air flow. The coils are dirty and reducing air flow.
2 - the barrier that separates the return and discharge, behind the register is dislodged (allowing air to recirculate in the plenum chamber).
3 - Improperly installed or defective freeze switch - there is a small thermistor on a pair of wires that pushes into the coils. This switch detects a freeze-up and cycles the compressor.
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javaseuf
Southern Cal
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BillyP wrote:A couple things can cause freezing up of the coils -
1 - poor air flow across the coils. Too many outlets closed (if a ducted unit) or only opening one end, of the discharge on a non-ducted unit. Dirty filter. Something in the duct blocking air flow. The coils are dirty and reducing air flow.
2 - the barrier that separates the return and discharge, behind the register is dislodged (allowing air to recirculate in the plenum chamber).
3 - Improperly installed or defective freeze switch - there is a small thermistor on a pair of wires that pushes into the coils. This switch detects a freeze-up and cycles the compressor.
 Hummm....Didn't I say the same things above???
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dougrainer
Carrolton
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Need a few things to help you. Year/make/model of RV. Make/Model of AC unit and IF ducted and does it have wall tstat controls or are the controls in the roof plenum. Doug
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