Hi, we have the 13,500 btu with ducted a/c. On my thermostat I have a low and a high setting on both auto and on.This past trip, we set it on high and felt the same air pressure and coldness coming out of the vents. After doing some site seeing, we noticed the a/c wasn't blowing out the same amount of air. I set it back down to low, which it seemed to be blowing at and then back up to high, I heard something feel like it wanted to kick on, but didn't. Luckily, it was cool that night and the low fan did work for cooling down the unit.Not sure if I froze up the fan, or something else. Any one have any suggestions?Thanks in advance.

Our AC's also have the hi/low switch. When we purchased our unit new, during the walk through the guy told us that most times running on low will make the unit freeze up. He suggested not using low, so I have never used it.

I use low 90% of the time. 13,500 but no ducts.

It primarily depends on humidity. Air conditioners have two functions, remove moisture from the air and cool the air. If the unit won't cycle because it is too hot or too much moisture is in the air, then the accumulated moisture freezes on the cools reducing the amount of air that can pass thru. The unit normally turns itself off to defrost the coils, called cycling. So, leave the fan on high until the rig is cooled down and much of the moisture has been removed. You may have to leave the temperature turned up (warmer) to allow the unit to cycle. Then you could turn the fan down to low. Listen for the unit to cycle. If it doesn't cycle, then turn the temperature up until it cycles on a regular basis and/or leave the fan on high.

I have a Duo Therm 15K BTU ducted on our 5th wheel. On high you hear the fan speed up and at the vents there is a small increase in air coming out but no where near what you would expect based upon how loud the fan gets. To me it sounds like it's running twice as fast as it does at low, so I would expect twice as much air coming out of the vents. That's my unscientific opinion.95 percent of the time we run our AC on low fan with the thermostat set at about 56 degrees. This seems to give us the coldest air. We always use the ceiling fan along with the AC and will use a couple of portable fans to direct the cold air into warm areas if needed.There is a sensor that sometimes comes loose (has happened on 3 different AC units). It turns the compressor on and off to prevent icing. It can be seen if you remove the AC ceiling cover and look up inside towards the evaporator fins. The sensor is round silver metal. It looks like a car signal relay.On some units it sits in a hole in the fins on others it clamps on to one of the tubes. It may be covered by metal tape. If it is loose or bad this will cause the unit to ice up and you won't get cooling.

We did get cooling, nice cold air, but the high fan seemed not to come on, just the low. O well, it is sitting out in the yard, going to look at it soon. I'll everyone know what I feel.

Air Condition high/low question | Good Sam Community

13 Replies

RJsfishin
Explorer
Aug 09, 2014
Seems perdy simple,.....on low the air will get colder, just logical thinking there. So, the slower moving.....colder air, will ice quicker, if icing is a problem. So, is there 3 reasons to use hi ?
1) you like the noise
2) to keep it from icing
3) to put more "push" behind the air so it will get to far away places :)
I do # 3,....but only when I am so unfortunate to be stuck in my MH in hot weather :(
dtzackus
Explorer
Aug 09, 2014
Ok, sorry for the lateness in my post. I went into the camper and the fan worked on both high and low for fan and a/c. Just got back from our latest camping trip and it worked all week on high. I guess it froze up as someone had mentioned. Thanks in advance....
dougrainer
Nomad
Jul 19, 2014
Dr Quick wrote:
As far as I know the only thing that HI of LO effects is the speed of the fan. It is like the fan speed in a vehicle, the faster the fan the quicker it should cool as it is moving more air. Coils usually will freeze up for three reasons, either the coil is dirty and it traps moisture which will then freeze, or system is low on refrigerant and that makes it a bit more efficient before it quits. Also there should be a T-stat on the coil that senses the temp there, so it should not freeze up. If your coil freezes up either sensor is out of position, or it is not working right.

Correct to a point. The LO fan speed travels air thru the fins slower and that allows the Evap to get colder and the AIR is colder as it has just a little more time to have the hot air removed and thus freeze IF the unit has no freeze sensor. On HI speed the air flows faster and turns over the hotter air faster to get cold. ONLY wall tstat systems have a freeze sensor. This is why the instructions state to run on hi cool to prevent freeze ups if there is no freeze sensor system. Doug
Dr_Quick
Explorer II
Jul 18, 2014
As far as I know the only thing that HI of LO effects is the speed of the fan. It is like the fan speed in a vehicle, the faster the fan the quicker it should cool as it is moving more air. Coils usually will freeze up for three reasons, either the coil is dirty and it traps moisture which will then freeze, or system is low on refrigerant and that makes it a bit more efficient before it quits. Also there should be a T-stat on the coil that senses the temp there, so it should not freeze up. If your coil freezes up either sensor is out of position, or it is not working right.
wa8yxm
Explorer III
Jul 18, 2014
I use HIGH all the time.. I will get to the explanation.

Some people say using HIGH will prevent icing (I disagree but that is only because I have seen exactly ONE case of icing that was caused by restricted air flow, and there was a lot more than ice that time (When the fan shut off and the ice melted NIAGRA FELL.

Now, the reaons I use high.

Many complain about the noise of the A/C.. Mine are ducted (Which does a good job of reducing the roar) but running full time on high, My mind very quickly filters the sound, and the sound of the A/Cs masks a lot of External noises I do not wish to hear. (Including the compressor) on my 13.5 ust now, I can not hear it (Trust me it is working) I can hear the 15 when Im in the other room but not the 13.5.
Terryallan
Explorer II
Jul 17, 2014
I usually keep mine on AUTO during the day, and low fan at night.
During the day, on AUTO the fan speeds up, AND then slows down as it feels like it needs to do. So I just leave it alone.
fla-gypsy
Explorer
Jul 17, 2014
My Coleman 13.5 is noticeably different in force of air in the ducted system on high. I leave my fan on all the time to help prevent freeze up.
dougrainer
Nomad
Jul 17, 2014
1. Wall tstat systems CANNOT freeze up regardless of fan setting---They have a freeze sensor that prevents that
2. Usually, on a wall tstat system if on Auto(Hi) the fan will run on high until it reaches within 5 degrees of the set temp then go to lo fan until it reaches the set temp and then the fan and compressor go off. When the tstat calls for cool again, it will go to lo fan first as long as the inside temp is within that 5 degrees of set temp. Doug
dtzackus
Explorer
Jul 17, 2014
We did get cooling, nice cold air, but the high fan seemed not to come on, just the low. O well, it is sitting out in the yard, going to look at it soon. I'll everyone know what I feel.
the_bear_II
Explorer
Jul 17, 2014
I have a Duo Therm 15K BTU ducted on our 5th wheel. On high you hear the fan speed up and at the vents there is a small increase in air coming out but no where near what you would expect based upon how loud the fan gets. To me it sounds like it's running twice as fast as it does at low, so I would expect twice as much air coming out of the vents. That's my unscientific opinion.

95 percent of the time we run our AC on low fan with the thermostat set at about 56 degrees. This seems to give us the coldest air. We always use the ceiling fan along with the AC and will use a couple of portable fans to direct the cold air into warm areas if needed.

There is a sensor that sometimes comes loose (has happened on 3 different AC units). It turns the compressor on and off to prevent icing. It can be seen if you remove the AC ceiling cover and look up inside towards the evaporator fins. The sensor is round silver metal. It looks like a car signal relay.
On some units it sits in a hole in the fins on others it clamps on to one of the tubes. It may be covered by metal tape. If it is loose or bad this will cause the unit to ice up and you won't get cooling.