Our Norcold refrigerator, model N621, is not working properly. The freezer is getting pretty cold but the refrigerator is hot. It is the same if it is on gas or shore power. We are not getting any error codes on the control panel. We have verified that the cooling unit is working and not leaking. Plus, we have checked the thermistor. There is plenty of hot air coming out of the roof vent and there doesn’t seem to be any blockage. Also, all the fuses are good. We have never had this problem before but we have not used it since July 2021. Any help would be appreciated. Thank you. —Molly, 2000 Nash 21-5R
To provide troubleshooting assistance we need more specific information and temperatures. Get a temperature gauge and find out the exact temperatures of the freezer and refrigerator, and what the ambient temperature is inside the rig.
More questions on your Norcold freezer and fridge
What do you have in the freezer? If it is empty, try putting a 5-pound bag of ice in it and see if the refrigerator temperature goes down. What is the temperature of the refrigerator compartment? A good rule of thumb is 34-36 degrees in the refrigerator and 0 degrees in the freezer.
How did you test the thermistor? It needs to be removed, set in a cup of ice water to get it down to approximately 32 degrees and use a multimeter to find the ohm reading. Have you tried moving the thermistor higher on the fins? Try using a 9-volt small fan to circulate air.
Next, how did you verify the cooling unit is working and not leaking? The only way to do this is to remove the refrigerator and run it for 24 hours and check the interior temperature and the cooling unit temperature.
A heat source, either a flame from the gas mode or a heating element from the AC mode, heats a solution of ammonia, hydrogen, water, and chromium sulfate. This solution turns to vapor and travels up a tube to the condenser fins, as you can see from this diagram, separates and goes through the freezer evaporator and flashes, drawing out heat. If you have a blockage at any of the tubes after the evaporator fin, the freezer will get cold, but the process cannot continue and the solution will often gurgle back down to the boiler vessel.
To check the cooling unit, a technician would use an infrared thermometer to follow the tubes and look for an extreme heat area in the tube. Typically, you will see the blockage if the metal in that area of the cooling unit has the black finish baked off and is rusted really bad.
If the rig isn’t level…
This is a common situation as owners bring their rigs to the house before a trip and plug it into the garage to cool the refrigerator down and get the unit loaded. Most driveways are slanted and since they are not sleeping in it, don’t realize it’s not level. There are no moving parts in an absorption refrigerator so the solution needs gravity to get back to the vessel when it turns back to a liquid. If the unit is out of level, the solution pools at one of the zig-zag corners and gets hotter and hotter until it starts to flake and eventually causes a complete block. Sometimes it’s just flaked enough to make it run insufficiently, but eventually, it will not cool.
Before taking out the fridge…
Before pulling the Norcold freezer and refrigerator out, I would suggest taking an air compressor and blower tip and clean out the entire back of the unit through the lower vent. Wear safety glasses, pull off the vent cover, and blow out all the dust in the lower area and up over the cooling unit as far as you can.
Also, if you have a roof vent, take off the cover and make sure it is clean and allows venting, even though you stated there was a lot of hot air coming out. When you take off the cover, look down the flue and make sure there is a clear path down to the bottom. I have seen situations where loose fill insulation has fallen from the side and is blocking what should be an open airflow behind the refrigerator. You might be able to see this from the bottom in some models.
Conduct a test on your Norcold freezer and fridge
Next, I would conduct a 24-hour hard test before pulling it out. This requires a 120-volt power supply connected directly to the wires of the heating element. Run it for 24 hours. If the unit cools like it is designed to, then it is in the module board or eyebrow board. When it is plugged in directly, it bypasses all the other modules and will tell you if the cooling unit is working and not blocked.
Check out the video we did at RV Repair Club here.
You might also enjoy this from Dave
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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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