Too cold

[tlmgcamp]

My 2022 Apex Nano has a Dometic DM2672. On our 4th trip with it laye last year, the fridge was at 25 degrees F and freezing stuff not meant to be frozen. The freezer was at 0 degrees F.

Under warranty, I believe they changed the thermistor. However, by the time the parts came in it was too cold outside to make a fair test. Now that we are having days in the 70's and 80's, I connected to shore power to see what happens.
The attached pics show how the thermistor is set. I have a thermometer on a shelf that is about 1/3 from the bottom of the fridge and won't go higher than 32 degrees F. Freezer is still at 0. At that time, it was 75 degrees outside with no AC on inside the TT.

Any ideas?

 

[SpencerPJ]

These refers simply do not play nicely with little to nothing in them. Then, my upper shelves tend to be colder than lower ones, and that changes dramatically as the door is open and closed. I don't think you will get a fair test until you are fairly well stocked, and have given it a day to equalize out.

 

[Rene T]

You may get a better reading by putting your thermometer in a glass of water on a shelf. Less chance of fluctuating as much than just having it on a shelf.

 

[Kirk]

the fridge was at 25 degrees F and freezing stuff not meant to be frozen.

That is a classic symptom of a failed or disconnected thermistor as when that happens the refrigerator goes into a constant cool mode and cools to the max capability. The use of a glass of water to stabilize the temperature is a valid step unless you are using a thermometer that has a remote sensor that does not require the opening of the door. Since the lowest temperature will be at the bottom, I would shift my sensor to the bottom shelf.

You might want to try moving the thermistor up and see if operating temperature changes. While it will probably get colder, that would at least tell you that the thermistor is connected properly and is reacting. it might be that the dealer didn't use the right thermistor as not all Norcold models use the same one, or it might also be that the problem that you took it in for was not the thermistor and the tech just swapped out the part most likely to have caused your problem. If it is still under warranty, be very careful in what you do as it could give them an excuse to void your warranty and charge you.

 

[Gary RV_Wizard]

Ditto the recommendation for placing the thermometer in a bowl or glass of water - it is necessary to stabilize the reading. Absorption fridges are notoriously uneven in cooling (there is no internal air circulation fan), even if the door remains closed. Better yet, add some jugs of water or something inside to chill and allow the fridge several hours to achieve a stable temperature.

I'll agree with Kirk that it could be a disconnected thermistor. The DM2672 will go into a constant-cooling operating mode if it gets no temperature feedback. Is that black electrical tape I see where the wire connects to the thermistor?

 

[Kirk]

Is that black electrical tape I see where the wire connects to the thermistor?

Sharp eye! It is not a rare thing for someone to replace a thermistor by cutting the wires rather than going through the sorting the new leads back through the openings in the chill box to where they belong. If that was done and the connection has failed, it might be the cause of your problems. I would take a close look at that tape and the connections.

 

[tlmgcamp]

Ditto the recommendation for placing the thermometer in a bowl or glass of water - it is necessary to stabilize the reading. Absorption fridges are notoriously uneven in cooling (there is no internal air circulation fan), even if the door remains closed. Better yet, add some jugs of water or something inside to chill and allow the fridge several hours to achieve a stable temperature.

I'll agree with Kirk that it could be a disconnected thermistor. The DM2672 will go into a constant-cooling operating mode if it gets no temperature feedback. Is that black electrical tape I see where the wire connects to the thermistor?

The black tape is holding the thermistor wire in place within the plastic slide. I noticed that moving the plastic slide downward was causing the bunched up wire on the drip pan to try to slide the thermistor upward within the slide. I was careful not to cover the thermistor itself with the tape

Sharp eye! It is not a rare thing for someone to replace a thermistor by cutting the wires rather than going through the sorting the new leads back through the openings in the chill box to where they belong. If that was done and the connection has failed, it might be the cause of your problems. I would take a close look at that tape and the connections.

The thermistor wire is continuous. The tape is on the wire to keep the thermistor from sliding inside the plastic piece that holds it to the cooling fin

 

[WME]

Never mind a cup of water for the thermostat, get 3 gallons of water, one for the freezer and 2 for the fridge. Thermal mass is what absorption fridges are all about.
Those blue cube battery fans do a lot of good too.

 

[Kirk]

The thermistor wire is continuous.

If you go to the plug connecting the thermistor to the circuit board, you can easily check the thermistor with an ohm meter to verify that it is good. From the Dometic service manual:

 

[tlmgcamp]

Thanks to all who offered assistance. Dometic has extended the warranty time to allow the fridge to be checked again. For what it's worth, I moved the thermistor from the warmest setting to the coolest setting and there was no temp change in the fridge. Hoping to resolve the issue in time for our trip in June

 

[John From Detroit]

Common issue with that type of device if the plug allows it is this

!! !! The plujg
. . .| | )The pins on the circuit board

Note only one pin would connect

 

[Kirk]

Let us know what happens next.

 

[Gary RV_Wizard]

Never mind a cup of water for the thermostat, get 3 gallons of water, one for the freezer and 2 for the fridge. Thermal mass is what absorption fridges are all about.
Those blue cube battery fans do a lot of good too.

You need to do both if the fridge is empty. The thermometer in water assures the thermometer gives a stable and accurate reading of its surroundings. The "thermal mass" helps stabilize the temperature in the fridge itself and thus improves the performance of the cooling unit's evaporators. If the fridge already has plenty of food and beverages, you don't need to add mass but immersing the thermometer is a liquid is still needed to get a reliable reading.

 

[Ray-IN]

Do I see a gap on the right wall? If it is, it might be allowing enough warm air into the area to be "fooling" the thermister into transmitting a false warmer temperature reading to the PC board.

 

[tlmgcamp]

Do I see a gap on the right wall? If it is, it might be allowing enough warm air into the area to be "fooling" the thermister into transmitting a false warmer temperature reading to the PC board.

I don't see the gap you reference. I will look at it in person when I get home. Can you circle it on my pic and send back?

 

[Ray-IN]

I don't see the gap you reference. I will look at it in person when I get home. Can you circle it on my pic and send back?

I don't know how to do that. What I perceive to be a gap is to the right of the aluminum fins, on the fridge wall . It appears as a tapered black line in your picture.

 

[Larry N.]

Ray, it's hard to be sure, but that "line" seems to me to be a grill in the wall but, being sideways it's hard to tell for sure.

 

[tlmgcamp]

I don't know how to do that. What I perceive to be a gap is to the right of the aluminum fins, on the fridge wall . It appears as a tapered black line in your picture.

I think what you are looking at is the angled view of the "warmer/colder" sticker in the other picture

 

[Ray-IN]

I think what you are looking at is the angled view of the "warmer/colder" sticker in the other picture

Thanks, you're right. Upon inspection that is the black down arrow seen at a slight angle. Sorry for the mis-direction.