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Dometic Fridge - Unusual Behavior


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I have a Dometic RM1350MIMX (double door, ice maker) that was installed new in my RV in 2012 when the 5th wheel was built. I have been living in the rig full time since the day I picked it up from the factory.

 

My freezer section has always been a little borderline - things would stay frozen but never got cold enough to keep ice cream hard. Didn't matter whether we were riding out sub-20's weather in winter or 100+ in the summer, ice cream was frozen but not hard enough to stay on a stick. The back and top of the freezer has always developed a lot of frost, especially around the ice maker. The refrigerator section has been extraordinarily stable, 38 degrees except right after loading it up with a fresh load of groceries.

 

Suddenly the top half of the freezer has become very warm. Everything is thawed above the middle shelf. The frost has melted, dripped from the ceiling of the freezer compartment and partially filled the ice bucket. But since the bottom of the ice bucket is on the floor of the freezer the water has refrozen and turned the ice cubes into a solid block of ice. The fridge temp is unchanged, still showing 38 degrees.

 

I've checked the usual things. The door gaskets are sealing and the fridge is level to within less than 1 degree. I doubt there is a problem with the cooling unit. If that were the case then both fridge and freezer would be warm. Or at the very least it would be the opposite of what I am seeing; the fridge would be warm while the freezer was okay. Or at least that is what all the trouble shooting manuals say.

 

Just as an experiment, I set the temp controller to the coldest setting. It has been several days now and the fridge is getting as low as 32 degrees during the night and first half of the day but the freezer is still warm in the upper half. At our current location the side with the fridge catches full sun (faces west) in the afternoon. I am seeing about a six degree rise in the fridge before the sun sets. But the recovery is rapid once the sun goes down, for the fridge not the freezer. Changing the temp setting seemed to have no effect on the freezer regardless of ambient temp.

 

So, have any of you come across this "reverse" problem? Got any ideas?

 

FYI: I contacted Dometic technical support via email. Gave them all the information above and they replied that for liability reasons they could not tell me anything. They suggested I take my rig into a certified service center. I can probably get a mobile repair service to come out but I wanted to get some more input on things I can try before shelling out the dough for that.

 

 

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The liability issues are that they have had a lot of these sorry refrigerators catch fire. The recall fix for them is nothing more than a patch. It does not stop the problem, but shuts the unit down in the event it gets too hot..

 

What you can do to help the unit is to install a 3" 12 volt DC fan on the interior to run full time and two 4" 12 volt DC fans in the exterior part. I wired the two added fans in series so that they ran 1/2 speed. I wired the fans to an internal lighted switch to operate them manually.

 

The added air over the condenser coils help the unit keep cooler in hot weather and the interior fan, evens the temperature in the box.

 

To help with the icecream, keep flat on the floor and against the back wall, lower left corner. It is the coldest spot in the freezer.

 

Since you live full time in the RV, I'd seriously consider converting to a 120 volt electric unit.

 

Ken

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I agree with your deduction that it isn't the cooling unit. It is pretty normal for a change of the temperature sensor to not make much impact upon the temperature of the freezer because all of the temperature control is done via a thermistor that is on the vanes of the chill box section. The refrigerant enters the cooling coils at the top in the freezer compartment an then cools as it passes through the coils, cooling first the freezer compartment and the remaining cooling then is applied to the chill box part of the refrigerator. The puzzle is, how can it fail to cool at the very top part of the freezer area? It sounds like it is somehow bypassing the upper part of the coils, or at least not removing any heat energy from that area. It is almost as though the upper coils were somehow insulated from the interior of the freezer.

 

Puzzling, to say the least.

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PS Can anyone recommend a specific interior fan?

 

Sure, Jack. This link is for a Norcold, but you can grab a Dometic specific unit as well. They're basically idential. Works wonders and comes with all the hardware you need to tie into the light or alternate 12v source.

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It's a little puzzling, but one thing I would check is to make sure you don't have anything in physical contact with the thermistor on the back fins there. Internal and external fan upgrades really make a big difference. Something to consider.

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The "coils" for the freezer transfer/remove heat from the compartment via a cooling plate at the rear of the freezer (where the screws are located). There is a heat transfer grease between this plate and the coils. Because you say "this has been marginal since new" I'd suspect maybe there is a lack of this grease of the coils are not pulled tight to the cooling plate. Try tightening the screws in the back of the freezer. To check the grease you'd have to pull the cooling unit.

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I at one time had one of those battery operated blue cube fans which was a waste of time. Then I put in two of those clip on 12V fans that attached to the fins. Those worked for awhile. I then just got fed up with the whole thing, threw out our Dometic & went with a Whirlpool residential.

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Ray makes a very good point. One other thing that you need to make sure of is that you don't need to defrost the freezer. It does sound as though your unit is much too warm for frost to be the problem, just be sure that it isn't as I have found that when our RV refrigerators are heavily frosted they do not cool well and the chill box does see more cooling. Since I live with an ice cream junkie, soft ice cream is one of the key things she uses to know when it is time to defrost.

 

While I doubt that frost is the problem, let's just make sure. :P

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Sure, Jack. This link is for a Norcold, but you can grab a Dometic specific unit as well. They're basically idential. Works wonders and comes with all the hardware you need to tie into the light or alternate 12v source.

Thanks for the link Yarome. I order the fans and look forward to firing them off.

Later,

J

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Thanks for all the help folks. Because of the sudden shift in behavior and the weird way it changed (the fridge compartment nearly freezing while freezer warm) I could only conclude that somehow the thermistor had become "compartmentalized" or insulated and was not calling for cooling as often as it should. So I unloaded the fridge compartment and reloaded it, careful not to push anything up against the coils and to leave gaps between items as much as possible throughout the fridge.

 

That did the trick. In just a couple of hours the ice maker started making ice again and all the soft stuff was firming up. By the next day everything in the freezer was rock hard. I don't know if I could ever reproduce the problem on purpose again but it does appear to have been an air circulation problem.

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