Ask Dave: Why does the RV refrigerator work on LP but not on 120-volt power?

Dear Dave,
The RV’s fridge (Norcold 7) will not cool on electric, but works fine on gas. —Rodney, 2019 Thor Chateau 22B

Dear Rodney,
Normally I would require a little more information for troubleshooting purposes such as actual temperatures of both operations including freezer temperature and inside ambient temperature. However, since your RV refrigerator does work to your satisfaction on LP, we can eliminate a few of the steps needed to help determine the issue.

First, since it does cool on LP, that tells me the cooling unit is not blocked and the liquid inside is turning into vapor and flashing like it is designed to. If the cooling unit was the issue and was blocked, it would not cool on LP. You would most likely hear a gurgling sound as the liquid hit the blockage and made its way back down the tube.

Next, it also indicates there is sufficient 12-volt power to the unit, which powers the  temperature settings, thermistor, and eyebrow board even when running on 120-volt power, and are all functioning properly.

It also indicates the heat sensor on the upper cooling unit coil and automatic shut off at high temperature is operating properly.

Malfunction of the 120-volt operation

So, it has to be a malfunction of the 120-volt operation. I would start by checking for 120-volt power at the plug just inside the rear vent cover.

This is connected directly to the circuit breaker at the distribution center and sometimes even “ganged” to the GFCI outlet inside. If the outlet trips, all the outlets are dead. If there is no power at the outlet, check the breaker and the GFCI reset button.

But if there is power at the plug, the next step should be conducted by a certified technician. They would check the glass fuse in the power module by making sure the shoreline cord is not plugged in, unplug the refrigerator, and disconnect the house batteries so there is no power coming to the refrigerator. Then they can remove the cover to the module and check continuity of the fuse. If the fuse is good, the next step would be to check the resistance or Ohm reading of the heating elements, which I would suspect is the issue at this point.

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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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