My RV’s refrigerator works fine until 9 a.m. then inside temp spikes. Why?

Dear Dave,
Another refrigerator question. I have a Norcold 2118 fridge that gives me fits. My rig is level and currently stationary, hooked up to my sticks-and-bricks power. I tried adding one of the fancy ARP controllers, but could not get the thermistor positioned. So I just wired the two inside fans and the two outside fans that came with the kit to a manual switch. For the outside fans I placed one low, sucking in air, and the other on the upper vent blowing out the hot air. I still have problems keeping the fridge cool when the weather gets warm.

Attached is a graph showing the temp(s) of the freezer and inside the rig. Granted, my fridge is currently pointed south. The day of the graph was overcast and you can see the temp remained much the same for the period. The fridge/freezer also seemed to be working fine, as you can see it cycling on and off until about 9 a.m., and then for some reason the temperature just keeps rising without the ambient temp rising in proportion. It looks as though the fridge never started a cooling cycle.

Hopefully, this all makes sense to you and you might have some suggestions as to what to try and resolve this. Thanks. —Greg, 2019 Montana 3560RL, Norcold 2118 fridge

Dear Greg,
Thanks for the detailed temperature comparison! First, on your Norcold 2118 refrigerator, the fans you installed won’t do much good from the bottom as there is too much blocking the path such as the rich liquid vessel and the cooling unit itself. Most of those fans are designed to be installed on the coil at the condenser, which typically means taking the unit out to get to the back. You must have the refrigerator in a slide room since you stated the other fans were in the side vent.

First test

The first test with any absorption refrigerator is to test it on 120-volt power and then on LP. I assume you are running it on 120-volt since it is plugged into your “sticks-and-bricks”? If you have it set on Auto, it will run on 120 volt as long as there is power, so set it to LP mode and see if there is any fluctuation. If there is none and it maintains temperature, we have isolated it to a power issue, not the cooling unit or other component.

This is where most troubleshooting guides have the “family tree”-type graphic that you go one way or the other depending on the outcome. Let’s go the direction of “runs good on LP, just not 120-volt power.” Since it is plugged to your house or garage, there is 120-volt power going to the distribution center. That provides 120-volt power through the circuit breakers to the appliances, including the roof air conditioner and the refrigerator. It is also providing 120-volt power to the converter, which charges your batteries and typically provides 13.2 volts constantly when the batteries are charged.

However, if your residential outlet is a typical 20-amp outlet, it may not provide enough power to the rig, especially if it is “ganged” to other outlets in the garage. A common misconception is, since I’m plugged in to power, everything 120 volt should work. Your rig is only getting 20 amps or less if there is another appliance plugged into the garage or an air compressor.

I recommend getting an outlet on a dedicated circuit. It can be 20 amps if you don’t run the roof air conditioner and other appliances. It is best to get a 30-amp dedicated outlet just like the campground.

Next, calculate what power the RV is drawing

Next we need to do some calculation on what your rig might be drawing.

The refrigerator will be anywhere from 6-8 amps, the converter will be another 6-9 amps depending on the size, and if you have the roof air on, Huh Oh, that can draw 14 amps! Most of the time the circuit breaker would trip in the garage. However, I have found some converters that simply do not provide a full charge when this happens and the batteries go dead even when it is plugged in.

Your refrigerator also needs 12-volt power for the thermistor, eyebrow board, and module. If the battery goes low, it will shut down. Since it does sense 120-volt power, it will not switch to LP in the auto mode. When you run the refrigerator in the LP mode, it reduces the amp draw and may be just enough for the converter to keep up.

Gremlins

The Gremlins, as I call them, are the variables you can’t see, such as, did the garage refrigerator, freezer, or air compressor start to cycle at the same time the refrigerator in your rig did and draw down the amps to your rig? Did the roof air cycle several times during this procedure? Also what you did not show is the ambient temperature outside.

The graph shows the temperature in the living room start at about 64 degrees then started to dip and at 9:00 it was down to about 54 degrees. That might mean the furnace kicked on or you had portable heaters that also added to the amp draw. In this situation I would plug into a dedicated outlet to get at least 20 amps, shut off the circuit breakers to everything except the refrigerator and converter, and see if that makes a difference. This will help to do an energy power evaluation in your rig.

One other item you could check is the heating element, as it could be weak and also have a Gremlin. Do you get any fault codes on the monitor panel at any time? The connections could be loose or corroded, or wiring is faulty. The heat element can be tested with an ohm meter and should register 58-68 ohms.

Back to the “family tree”: What if it performs the same on LP?

If the temperatures are the same on both modes, then it is in a component within the cooling unit or modules. The first test is to remove the thermistor and place it in the freezer, setting the temperature at the lowest setting.

Allow the unit to operate for 3-4 hours and measure the temperature, at which time the back of the freezer plate should be cold. The freezer should be between -5 to -10 degrees F. The fin temperature should be 15-25 degrees F. One thing you did not provide is the temperature in the refrigerator. It should be at 40 degrees F.

You can also test the thermistor by placing it in a cup of ice water which will bring it down to 32 degrees or colder, and do an ohm test. Your owner’s manual should have the values; however, here is a chart from a Norcold 1200 model.

One of the tests a certified technician would perform is  a 24-hour direct test, which is hooking a 120-volt source to the heating element by splicing the wires. This is not recommended by Norcold for the average RV owner. This bypasses the thermistor, eyebrow board, and module. If the unit works for 24 hours, it is not the cooling unit. If it performs the same as you are seeing now, the cooling unit has a blockage in the coil and needs to be replaced or the refrigerator itself. But if it works as designed, then we need to verify the thermistor and the module board.

This is as far as we can go until we get more data on what is happening during these tests and procedures.

 You might also enjoy this from Dave 

Why is my Norcold freezer cold, but fridge hot?

Dear Dave,
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

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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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