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Old 12-08-2021, 10:33 AM   #1
djac13
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My AC unit keeps freezing

My dometic 59516 AC unit keeps freezing. I've pulled the unit open and the evaporator coils have a tone of ice on them.

I've done some reading and it looks like a few things are recommended;
1. clean the coils - any recommended clears besides water and soap? (the unit doesn't really look that dirty)

2. ensure the flow divider is sealed so the unit is not sucking the cold air in to cool. (I need to seal this up a little for sure)

3. clean airfilter - which I've replaced

4. humidifier - I'm in Florida right now so yeah, it's freak'in humid. I have a small humidifier by the AC unit.

Any advice is welcome.

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Old 12-08-2021, 10:48 AM   #2
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#2 likely has the most influence on this.

If no other causes are evident, low refrigerant can cause frozen coils too.
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Old 12-08-2021, 11:55 AM   #3
chuckster57
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Where is the freeze sensor? Placement can affect performance.
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Old 12-08-2021, 12:02 PM   #4
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Quote:
Originally Posted by chuckster57 View Post
Where is the freeze sensor? Placement can affect performance.
Yes this what was wrong with one of my ACs is the frost sensor became dislocated from the cooling coils
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Old 12-08-2021, 03:14 PM   #5
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The freeze sensor could be part of it, but relative humidity is likely the biggest culprit. A dehumidifier will help (hopefully you meant dehumidifier and not humidifier like you wrote in your post). I would pick up an inexpensive hygrometer/thermometer and monitor humidity levels.

When humidity is high in my unit, I can see condensation on the ceiling vents and keep an eye out for freezing and double check for open windows, vents or door. Cooking can also dump a lot of humidity into the air since the major by-product of a propane burning appliance is water vapor (1.6 lbs of moisture for every 1 lb of propane burned).

The one and only time (so far) that I had a freeze-up, the sensor wire had fallen out of the coil. It just pokes in there and can fall out pretty easy.
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Old 12-08-2021, 04:32 PM   #6
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Could be you don't have your fan on high speed and you have the cooling set fairly towards the warm... like 78-80F etc.
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Old 12-08-2021, 06:47 PM   #7
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We had issues with freezing, but haven’t for a long time.
Steps taken;
Sealed unit so cooled air wasn’t drawn back in.
Don’t open “Quick Cool” vent on unit.
Have dehumidifier and keep interior humidity around 40%.
Run AC fan on high always.
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Old 12-09-2021, 07:23 AM   #8
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Quote:
Originally Posted by djac13 View Post
My dometic 59516 AC unit keeps freezing. I've pulled the unit open and the evaporator coils have a tone of ice on them.

4. humidifier - I'm in Florida right now so yeah, it's freak'in humid. I have a small humidifier by the AC unit.
I'm going to assume you mean dehumidifier -- otherwise, there's your problem.
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Old 12-12-2021, 04:56 PM   #9
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Hahahha, yeah I meant dehumidifier
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Old 12-12-2021, 04:58 PM   #10
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My sensor is in the middle closer to the top.
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Old 12-12-2021, 05:24 PM   #11
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We used to have this problem all the time in our old rig. At first, I would just solve it with a hairdryer and a bucket. Then I started doing something different, which may or may not have been voodoo: if I pulled into a campsite, and the interior cabin temp was up around 100, and I set the thermostat to 80 and let it run, it would freeze up; but if I set the thermostat to 95, and let it cycle a couple times before lowering that to 90, and eventually working my way down to 80 in that fashion, I never had a freeze up again.
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Old 12-12-2021, 06:34 PM   #12
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Update also, I removed all the ice and there was a thick section, I got it all cleaned, I taped up all the gaps or little holes which was more than I thought and finally we changed our fan setup from auto to high from morning to night. So far it’s been a lot better for sure.
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Old 12-12-2021, 06:38 PM   #13
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Good deal. Having the return sealed off from the discharge is somewhat critical. Might want to check with Dometic, but I thought the sensor needed to be closer to the bottom of the coils.
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Old 12-12-2021, 09:41 PM   #14
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Quote:
Originally Posted by djac13 View Post
Update also, I removed all the ice and there was a thick section, I got it all cleaned, I taped up all the gaps or little holes which was more than I thought and finally we changed our fan setup from auto to high from morning to night. So far it’s been a lot better for sure.
Higher airflow does help. When we had icing problems we used to open our dump panel to help keep the icing from forming. Also, check your coil fins, and if any of them have been smushed flat from handling (or ice removal, which was our error), you can get an inexpensive "repair comb" to separate them again and restore full airflow.
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Old 12-12-2021, 11:29 PM   #15
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When you run your ac, run it with the fan set to high and not auto in the humid conditions. This will prevent the unit from freezing over. Worked for me in the past when I ran into same issue.
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Old 12-13-2021, 03:30 AM   #16
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Thanks chuckster57, I’ll check with them.

Yeah RVGator, we are now doing that also, thanks for the tips all.
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Old 12-20-2021, 06:14 PM   #17
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I changed the location of the freeze sensor & thoroughly cleaned the coil fins with appropriate chemical.
No luck. It kept freezing up fast.
We called a RV service tech & he tested the unit. There was a freon leak. It had to be replaced.
We replaced it with another Dometic 15k ducted unit & extended the 2 year dometic warranty to 5 years for about $100 more.
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Old 02-28-2022, 06:46 AM   #18
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well, I think it was a combination of newbie living in a humid warm climate and newbie for the RV life but with all of your help, it's been working fine since. Although we haven't used it much recently but hope too soon.
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Old 02-28-2022, 07:18 AM   #19
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I've had some relatives that have had issues with their A/C systems and refrigerator for common issue. With the A/C unit you arrive at a hot humid place and turn on the air. Or you throw open the doors and windows at night then wait until it gets really hot and humid to turn it on. In both cases the entire interior is hot and humid. The unit now has to pull not only the heat but also the moisture not only from the air but also from the rugs, furniture , beds, etc.

The other common issue I've seen is either leaving the door open or constantly comming in and out. My DW's brother would leave the door open and tell me it's ok "because the electric is paid for". Then every evening he'd complain about the A/C being froze.

I've seen the same issues with refridgerators. Folks, especially kids, will stand and stare in to the fridge with the door wide open, Then they can't understand why the coils are iced up and the food is warm. I'm not saying this is your issue but just making anyone reading aware that the above can cause issues.
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Old 02-28-2022, 01:34 PM   #20
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Quote:
Originally Posted by djac13 View Post
My dometic 59516 AC unit keeps freezing. I've pulled the unit open and the evaporator coils have a tone of ice on them.

I've done some reading and it looks like a few things are recommended;
1. clean the coils - any recommended clears besides water and soap? (the unit doesn't really look that dirty)

2. ensure the flow divider is sealed so the unit is not sucking the cold air in to cool. (I need to seal this up a little for sure)

3. clean airfilter - which I've replaced

4. humidifier - I'm in Florida right now so yeah, it's freak'in humid. I have a small humidifier by the AC unit.

Any advice is welcome.

2021 cougar; 32BHS
Silverado 3500
Is there a freeze sensor installed? It should be pushed into the coils, if so maybe it has fallen out. You can look in the compartment where the filter is and see if you can locate it.
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