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Old 06-25-2018, 07:42 AM   #1
sgpa4boys
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A/C freeze up

Hi all. Have a 2012 sprinter 311bhs. The last 2 years we have really struggled with freeze ups of the a/c. Had it cleaned and washed this week and still doing it. Any suggestions?
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Old 06-25-2018, 09:46 AM   #2
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Evaporator freeze up is usually a sign of one or more things
1. Not enough air flow across the evaporator.
2. Freon charge is low.

Not enough air flow could be something as simple as the fan speed being set on low speed instead of high speed, especially if you are trying to operate the unit in very high humidity conditions. It could also be a dirty evaporator which doesn't let enough of the return air flow across it. Another possibility is having some of the outlet air vents closed off....if you have the type of outlets that allow you to close them off or almost closed off.

Number two possibility ( low refrigerant) means that there is a leak in the refrigerant circuit. This could be in any of the components.....evap, condenser, any of the tubing, compressor lines, etc. If there is a refrigerant leak, it is usually cheaper to buy a new A/C unit than to have the existing one repaired. They don't usually come with service ports installed when new, and when you add the cost of adding them AND fixing the leak, a new unit is a cheaper option usually. Check the easy stuff first....air flow issues. It could also be a fan that is dirty or the brains are failing, causing the fan to run at a reduced speed, thus not enough air flow.
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Old 06-25-2018, 09:48 AM   #3
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Our A/C is a ducted model. There is a damper on the front that allows air to flow straight out (open). Or, diverts to the ducts (closed). If I leave the damper open during the day, I donít have freeze ups.

You should also make sure the filter is clean. The idea is to get good air flow.
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Old 06-25-2018, 01:30 PM   #4
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In addition to low airflow and fan speed, dirty filters, high humidity and other airflow problems, freeze-ups can be caused by a faulty freeze detector or an unplugged freeze detector. Inside the return airbox is a "freeze detector" that is inserted through the fins of the evaporator. If the unit is freezing from water accumulation in the evaporator fins, then the "freeze detector" should be pulled from the fins and reinserted a bit higher or lower. This may not be your problem, but deserves a quick "look-see"...
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Old 06-25-2018, 02:49 PM   #5
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Unit was just cleaned inside and on top. Air flow is good and always runs on high with all vents open. Guess I will just keep operating until she gives out. Thanks
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Old 06-25-2018, 03:49 PM   #6
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Quote:
Originally Posted by JRTJH View Post
In addition to low airflow and fan speed, dirty filters, high humidity and other airflow problems, freeze-ups can be caused by a faulty freeze detector or an unplugged freeze detector. Inside the return airbox is a "freeze detector" that is inserted through the fins of the evaporator. If the unit is freezing from water accumulation in the evaporator fins, then the "freeze detector" should be pulled from the fins and reinserted a bit higher or lower. This may not be your problem, but deserves a quick "look-see"...
Thanks John......that one slipped my mind when I posted!
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Old 06-25-2018, 06:44 PM   #7
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One other cause not mentioned is not keeping the door closed. Kids will often leave the door open or stand in the doorway with the door open. FWIW
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Old 06-25-2018, 07:03 PM   #8
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Reading the responses to the OP's problem and rereading the OP's first post, he says, " The last 2 years we have really struggled with freeze ups of the a/c." Looking at that part of the post, I'd suspect it's not a Freon leak. If it was a leak, there probably wouldn't be a 2 year history of the problem. With the small amount of Freon in rooftop air conditioners, even a "very small" leak would have stopped all cooling capacity in 2 years... So, my guess is that it's something else. Either low air flow, probably coupled with high humidity, inability to move air through restricted ducting (again, low air flow), dirty filters, leaking air box (hot air mixing with cold air in the hot air return) or the freeze sensor.

I haven't seen an A/C that works properly when new and leaks Freon to a point, then stops leaking for 2 years. My experience has been that once a leak starts, even a "minutely small leak" will empty the entire system and stop all cooling within 3-6 months.

Maybe I've had a "sheltered life" and I admit I haven't seen it all, but I don't think this is a Freon leak. The only "real way" to test it is with an ammeter and check the load on the compressor. But, I'd strongly suspect it's not a Freon leak.
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Old 06-25-2018, 07:31 PM   #9
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Quote:
Originally Posted by JRTJH View Post
Reading the responses to the OP's problem and rereading the OP's first post, he says, " The last 2 years we have really struggled with freeze ups of the a/c." Looking at that part of the post, I'd suspect it's not a Freon leak. If it was a leak, there probably wouldn't be a 2 year history of the problem. With the small amount of Freon in rooftop air conditioners, even a "very small" leak would have stopped all cooling capacity in 2 years... So, my guess is that it's something else. Either low air flow, probably coupled with high humidity, inability to move air through restricted ducting (again, low air flow), dirty filters, leaking air box (hot air mixing with cold air in the hot air return) or the freeze sensor.

I haven't seen an A/C that works properly when new and leaks Freon to a point, then stops leaking for 2 years. My experience has been that once a leak starts, even a "minutely small leak" will empty the entire system and stop all cooling within 3-6 months.

Maybe I've had a "sheltered life" and I admit I haven't seen it all, but I don't think this is a Freon leak. The only "real way" to test it is with an ammeter and check the load on the compressor. But, I'd strongly suspect it's not a Freon leak.
I disagree, but my wife says I've lead a sheltered life as well!!!
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Old 06-28-2018, 08:25 AM   #10
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What is a freeze sensor?
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Old 06-28-2018, 09:23 AM   #11
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If I'm not mistaken, basically a sensor that will detect when the evaporator is too cold because of lack of airflow and or very high humidity and is starting to freeze up. It will stop the compressor from running. When the compressor isn't running and the fan is still running, eventually the air that is flowing will become warmer and warmer and eventually thaw out the frozen evaporator. If the freeze sensor has been bumped or fallen away from where it should be located, it cannot detect the evaporator freezing up and the compressor continues to operate...making it freeze even more.
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Old 06-28-2018, 05:50 PM   #12
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So I noticed a wire hanging down in the evaporator area that looked like the end was possibly a sensor. I pushed it into evaporator fins and it ran perfectly for 5 hours this evening. Keeping fingers crossed
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Old 07-03-2018, 12:44 PM   #13
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On our last weekend camp out the Dometic 15K unit froze up.

I figured it was the humidity+fan switching to low as it got close to the set point.

I did some research and found the major culprits for my scenario and did some investigation.

I checked the filter and coils and they looked brand new, which they basically are, the AC unit is just over 3, but we rarely camp when it is necessary.

There were plenty of places where cold air could get sucked into the return plenum, so I got some metalized duct tape and sealed that up.

I verified the freeze sensor was stuck into the evaporator.

Then I checked the temperature differential, between discharge and return and it was only 8 degrees.

I contacted Dometic, from their customer support page and they suggested I do the things I had already done and I once again mentioned the temp differential, so they asked for compressor current draw.

I am still waiting for a response to that information.

It is nice they are willing to engage with me and I am hopeful they will do something to help... I have seen many posts on the web where folks had similar problems, with the same unit and they were replaced under warranty, some more than once.

Good luck with yours.

-Brian
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Old 07-08-2018, 09:13 AM   #14
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Ac freeze

We had a brand new unit and the AC was freezing over. We were traveling Yellowstone in 40 degree plus temps.

Dealer ship said nothing wrong.

This year pull out of storage and first weekend out and was woken up in night. Temp outside 20 C. Temp inside 22. And it was 230am. Of course ac frozen over

Too back to dealer explained. ...This time they took a look. And ended up replacing the whole unit and some sensors.

Works perfect now. Airflow at registers is better and it cycles properly.

I guess my point is sometimes you have to be the squeaky wheel.
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Old 07-08-2018, 05:14 PM   #15
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Originally Posted by sgpa4boys View Post
Unit was just cleaned inside and on top. Air flow is good and always runs on high with all vents open. Guess I will just keep operating until she gives out. Thanks
Guessing they did not actually clean the evaporator coil which is the problem most of the time. 27 years fixing these and everyone says they cleaned it all but usually did not get the evap clean.

Not a freon leak.

Possible air short circuiting to return air as mentioned. How close was the amp draw to the RA on compressor tag?
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Old 07-09-2018, 10:08 AM   #16
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Guessing they did not actually clean the evaporator coil which is the problem most of the time. 27 years fixing these and everyone says they cleaned it all but usually did not get the evap clean.

Not a freon leak.

Possible air short circuiting to return air as mentioned. How close was the amp draw to the RA on compressor tag?
I have the same problem with a 2013 Coleman Mach 15. I cleaned the evaporator personally. I checked/ re taped all of the ducts. I have all ducts open. I have freeze up and have moved the freeze switch up and down every possible way. I run on high, fan always on. I checked the amps on black wire to compressor and it was a steady 9.7/9.8 draw. I have ordered a new one, but wish I could solve the problem with this one. 2013 Keystone Fuzion M300 owner.
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Old 07-09-2018, 05:44 PM   #17
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After you check the condenser fins and they are clean, If your AC split temp is low( temp of camper vs temp of air from ducts-less than 10 degrees) then it is low on refrigerant. Yes, I am AC certified.
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Old 07-09-2018, 07:02 PM   #18
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Quote:
Originally Posted by B-O-B'03 View Post
On our last weekend camp out the Dometic 15K unit froze up.

I figured it was the humidity+fan switching to low as it got close to the set point.

I did some research and found the major culprits for my scenario and did some investigation.

I checked the filter and coils and they looked brand new, which they basically are, the AC unit is just over 3, but we rarely camp when it is necessary.

There were plenty of places where cold air could get sucked into the return plenum, so I got some metalized duct tape and sealed that up.

I verified the freeze sensor was stuck into the evaporator.

Then I checked the temperature differential, between discharge and return and it was only 8 degrees.

I contacted Dometic, from their customer support page and they suggested I do the things I had already done and I once again mentioned the temp differential, so they asked for compressor current draw.

I am still waiting for a response to that information.

It is nice they are willing to engage with me and I am hopeful they will do something to help... I have seen many posts on the web where folks had similar problems, with the same unit and they were replaced under warranty, some more than once.

Good luck with yours.

-Brian
X2 to sealing the duct-work with the aluminum duct tape, solved 99% of your freeze up issues.
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Old 07-10-2018, 04:08 AM   #19
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Originally Posted by theboneskes View Post
After you check the condenser fins and they are clean, If your AC split temp is low( temp of camper vs temp of air from ducts-less than 10 degrees) then it is low on refrigerant. Yes, I am AC certified.

I failed to mention that in my post yesterday. The temp split is low, usually 9 to 11 degrees difference at best depending upon the freeze issue. I have purchased a "self piercing valve" and plan to install it, but I have not found anyone that sells small supply of R 410a refrigerant. I have the gauges and pump, but no Freon. Could you offer some advise? If I can get it working properly, I may install it in the garage.
I am not certified, just trying to get by.
Thanks
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Old 07-10-2018, 04:52 AM   #20
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I failed to mention that in my post yesterday. The temp split is low, usually 9 to 11 degrees difference at best depending upon the freeze issue. I have purchased a "self piercing valve" and plan to install it, but I have not found anyone that sells small supply of R 410a refrigerant. I have the gauges and pump, but no Freon. Could you offer some advise? If I can get it working properly, I may install it in the garage.
I am not certified, just trying to get by.
Thanks
In my opinion installing a "self piercing valve" is installing another leak. You state that you have a pump and gauges. No offense but do you know how to use them? Just adding refrigerant doesn't fix the leak, it just adds more refrigerant to leak out. Overcharging the system can do more damage. To properly recharge the leak has to be fixed, the system dried out evacuated properly, a proper charging valve installed (a schrader valve welded into the line,) and then a proper charge with the proper amount of oil for the system. On small self contained systems the amount of charge is critical and a few ounces under it won't cool and few over it will destroy the compressor. It's really not a DIY project in my opinion.
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