I’ve been testing the A/C out on my new trailer the last couple days. It doesn’t seem to be blowing near what previous units I’ve owned do and doesn’t cool the trailer very well. From what I can tell I think the blower is running backwards. Being a 12 volt fan it seems like a simple fix. Any pointer from anyone? Thanks.
Fan running backwards.
- Thread starter RiverManJ
- Start date
The fan is 110 volt. Make sure the blast gate at the A/C is closed to have it go throught the vents.
wdk450
Well-known member
Brand and model of AC unit? You may have to remove the rooftop shroud to find the label. Manuals for most all in our library:
I was running the fan on auto. I’ll try it on high this weekend. Right after I posted originally I pulled the intake panel off and saw the condenser was froze solid. I’m guessing that was the airflow issue, not that the fan was backwards. It just seemed like the air was swirling instead of blowing. Would closing the blast doors freeze the condenser?
wdk450
Well-known member
The Dometic AC's have a "freeze sensor" that turns off the compressor when the evaporator (cooling) radiator freezes up due to high humidity and low air flows, but allows the main air movement fan to keep running to automatically defrost the evaporator. This sensor clips onto the evaporator cooling metal tubing, but often comes off due to road vibrations when travelling. Your evaporator being frozen solid will definitely block cooling air flow.
Do a forum thread search on the term "freeze sensor" ( the forum search is the magnifying glass icon at the top right of any forum page).
Do a forum thread search on the term "freeze sensor" ( the forum search is the magnifying glass icon at the top right of any forum page).
Roller4tan
Well-known member
After many years of AC use, I have learned that the cheapo filter does very little to stop dust, etc. from collecting on the condenser. Some of it can be vacuumed from below, but its best to take the cover off on the roof, separate the foam covers and clean from there. That'll help the airflow.
wdk450
Well-known member
My 2008 production Bighorn has the older style (looks like a round metal auto turn signal flasher) freeze sensor. Your picture shows the newer style black small probe tip style sensor. The only reason for ANY electrical connection to the condenser is the freeze sensor. Pumped cold freon goes through the condenser copper tubing, blown air from the fan goes perpendicular through the condenser. Ice blockage can be caused by high humidity, dirt blocking condenser and/or inside air filter, air moving between the intake and cold air sections of the inside roof box sections (intake section surfaces should be well sealed with duct tape), and having roof vents and windows open when running the AC (this causes inside air to possibly keep drawing in humidity from outside air).
BTW, besides coming mechanically disconnected from the condenser, freeze sensors have been known to fail. I think they should show an open circuit only when the probe temperature is near freezing, or below.
BTW, besides coming mechanically disconnected from the condenser, freeze sensors have been known to fail. I think they should show an open circuit only when the probe temperature is near freezing, or below.
Last edited:
2019_V22
Well-known member
That older metal style is probably a Bi-Metal on off thermal disc. Yes the one in my pic was part of the kit I added to upgrade from analog controls, and is a resistance style thermistor. That paired with the Micro Air thermostat, will actually show you the degrees in Fahrenheit on the screen for that freeze sensor.
But actually the Freon is pumped by the compressor as a gas to the condenser where it's condensed to a hot liquid, mostly cooled by the condenser, then flows to the metering device, whether it be capillary tubes, or a TXV. Once it enters the evap coil the liquid boils off to a vapor, which produces the "cold" affect, it then absorbs the heat transferred to that vapor through the fins of the coil, the now "super heated" vapor returns back to the compressor to be condensed to a liquid and start the process over.
But actually the Freon is pumped by the compressor as a gas to the condenser where it's condensed to a hot liquid, mostly cooled by the condenser, then flows to the metering device, whether it be capillary tubes, or a TXV. Once it enters the evap coil the liquid boils off to a vapor, which produces the "cold" affect, it then absorbs the heat transferred to that vapor through the fins of the coil, the now "super heated" vapor returns back to the compressor to be condensed to a liquid and start the process over.
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