Front AC Freezing up

[AWF1945]

Im still in Alabama and have had to start using air conditioning more. The thermostat on zone 1 controls front AC. The temp setting is way off. Example, inside temp shows 83° AC set to cool 73° it never makes it without freezing up! Apparently its not cycling through defrost mode during cooling process. Any ideas or tricks? Rear unit works great.

[bclemens]

Make sure the return air is not clogged in any way. Is the fan "ON or Auto"?

[TURBS]

Frost sensor may have fallen off.



2008 2500hd Duramax
2015 Columbus 320RS
2016 nights camped "0"
2015 nights camped "34"

[R3Jones]

Along with the other suggestions, make sure there are no holes in plenum between the air exhaust and air intakes.


-R.Jones
Nitro 31FQSL

[TURBS]

Does your unit have the quick cool dump?


2008 2500hd Duramax
2015 Columbus 320RS
2016 nights camped "0"
2015 nights camped "34"

[AWF1945]

Thanks for the replies as always.. yes air return in good shape. Unit was set on auto, yes sensor is in place, higher than one shown in picture. Mines in the center of coil located in the middle. Turbs, quick cool dump? you're talking bout defrost mode right? not sure I've heard it called that. At any rate something is not doing what its supposed to. Works great in lesser Temps.. rear unit works great no matter what the temp.

[TURBS]

Does your ceiling cover look like this?


2008 2500hd Duramax
2015 Columbus 320RS
2016 nights camped "0"
2015 nights camped "34"

[AWF1945]

Turbs, what your showing looks to be from a duo therm ac unit. Mine are Coleman Mach Airxcel 4700 series

[TURBS]

Ok well I didn't know what you had and was wondering.

3 causes of freeze up

1) not enough air flow or restricted air flow. I.e. To many vents shut off or a blockage in the ducting.
2) frost sensor inoperable or fallen off.
3) unit is low on refrigerant.


2008 2500hd Duramax
2015 Columbus 320RS
2016 nights camped "0"
2015 nights camped "34"

[AWF1945]

Thermostat reading is different than what I get from temp gun as shown. Also wall senor different from thermostat. I beginning to think I have a bad thermostat. The rear ac unit zone 2 is right on the money.

[bob dirt]

Originally Posted by TURBS

Ok well I didn't know what you had and was wondering.

3 causes of freeze up

1) not enough air flow or restricted air flow. I.e. To many vents shut off or a blockage in the ducting.
2) frost sensor inoperable or fallen off.
3) unit is low on refrigerant.


2008 2500hd Duramax
2015 Columbus 320RS
2016 nights camped "0"
2015 nights camped "34"

4) restriction in refrigerant line
5) thermostat not shutting off compressor

sounds to me like your stat is keeping compressor on too long bringing the evap temp below freezing

[TURBS]

Originally Posted by bob dirt

4) restriction in refrigerant line
5) thermostat not shutting off compressor

sounds to me like your stat is keeping compressor on too long bringing the evap temp below freezing

Thanks Bob [emoji106]

[bclemens]

Could be location of remote sensor.

If I read your pictures correctly...the t-stat says 74, but in fact the room is 68? The T-stat is not really reading the temps in most cases because we put it behind a door. There is a little plastic "eye" looking thing. Either that is malfunctioning or something is keeping it artificially heated.

[DocRob]

While any AC can freeze up under the right conditions I am concerned that your freezing unit may not be charged properly since your back one is working fine under the same conditions. Usually happens when the charge gets a little low due to a pin hole somewhere in the system but I hope I'm wrong since they can be very hard to locate.

[TimVWulp]

Originally Posted by bclemens

Could be location of remote sensor.

If I read your pictures correctly...the t-stat says 74, but in fact the room is 68? The T-stat is not really reading the temps in most cases because we put it behind a door. There is a little plastic "eye" looking thing. Either that is malfunctioning or something is keeping it artificially heated.

2X any heat source that may influence the remote sensor (television, coffee pot, computer monitor ext) anything that can produce heat. what is the wall temp remote temp sensor mounted to? Remote temp sensor battery's are in good shape if sensor has them? Dose the coil freeze up with out door air temps above 75-80 deg? Or at night? Air filter is clean Cooling coil is clean? fan speed is on high or low? Air flow is very important for the air conditioner to function properly. Low room air temps of 65-68 deg will lead to coil freeze ups as the refrigerant temp inside the cooling coil will or may drop below freezing with this cold of air temp entering the cooling coil. AC units are designed to operate at room air temps of 72-75 deg.

Hope This Helps Tim

[AWF1945]

Originally Posted by bclemens

Could be location of remote sensor.

If I read your pictures correctly...the t-stat says 74, but in fact the room is 68? The T-stat is not really reading the temps in most cases because we put it behind a door. There is a little plastic "eye" looking thing. Either that is malfunctioning or something is keeping it artificially heated.

The third picture is the small sensor located near the thermostat. You are correct the thermostat is enclosed and ubable to correctly diaplay inside temp. I left the door open today and it gas worked fine.

Its not been as hot today but has cycled fine. Both output temps of both ac units are the same. I don't believe there's a freon leak. I believe the problem lies within the thermostat.

Yes, I did run fan on high today, yes the filters are clean, thanks for the replies.

[AWF1945]

I'm going to give the sensor the hair dryer test to start compressor. It should within minutes equalize and shut off.

[AWF1945]

Okay heres what I believe is happening. The hair dryer test confirms the senor is working as it should. Notice in the picture the location of the sensor and the thermostat. When taking temperatures with my temp gun I noticed the interior bulkhead temp was 86°. That sensor is giving a false reading due to its location. I took several readings today. When that thermostat door is closed and the sun is shining on that outter wall the sensor temp was 7°-10° higher than actual room temp.. thus AC confused and not cycling as it should.

Now with all that said. I opened thermostat door, left it opened all day... once the sun was no longer on that wall I had consistent readings like my earlier photos. Sounds crazy right... not really.

You see the bedroom sensor is in a perfect location and doesn't have to deal with any variations in temperature other than actual room temp itself. Now that I'm aware of this I will leave the door open to help prevent heat buildup or relocate sensor.

Both front and rear units are putting out a consistent 20-23° in compressor mode. At one point I got an 18°...

[AWF1945]

Opps forgot to insert picture

[TimVWulp]

Glad to hear that you were able to figure out that the sun was causing the temp problem. Thanks for letting us know what you found.

Tim