Friday, June 2, 2023


Ask Dave: Why do fridge fins ice up and then drip tray overflows?

Dear Dave,
We seem to be having an issue on and off with our Norcold N821L (I think that’s the model) fridge. This only seems to happen when we’re “stuck” down here in Houston. When we’re in home country (Carson City, NV, 5,000 ft. elev.) this never happens. The fins in the reefer ice up (normal I guess) but the water tray beneath them will fill up to overflowing, which is a problem. I go out and check the evaporation tub (my name) and sometimes it’s full. I empty it. We’ve blown out the tube that the water runs down in, and even blown out that useless plug at the end. My wife has the fridge fan aimed right at the fins now and we leave it running between foodstuffs for circulation. What could be causing this? It’s currently running on 120AC. —Tommy, 2012 Arctic Fox 25Y

Dear Tommy,
We have done quite a few videos on that model at the RV Repair Club and a bunch of articles about efficiency in hot weather. The fins in the refrigerator cabinet will collect frost. However, they should not ice up as much or as often as you are referring to. My first thought is it’s not happening in NV because at 5000 feet elevation, it is much cooler and less humid. Therefore, your refrigerator is not working as much, so there’s less chance of frosting over and icing up. In Houston, it’s hot. Even though they claim it’s a dry heat…it’s not!

Check out my recent post of the refrigerator that was icing up in the freezer section and do the test with the dollar bill and the door seals. If warm, moist air enters the refrigerator cabinet, it will create high condensation and more than normal frosting as well as icing.

Dollar bill test of refrigerator door seal.

Fridge drip pan

As for the drip pan, that is not a normal collection of moisture. I also noticed ice in the tray, so even blowing out the line would not help with flow as ice would be restricting it. A suggestion would be to get rid of the filter that sticks out the outside refrigerator vent and just let it flow.

I would also suggest trying to replace the drain hose as it can get kinked or collapsed and restrict flow. Blowing it out with air is more pressure than a water gravity flow, so it could still restrict normal flow. Also check to make sure the drain hole in the tray is cleared as the hard water usually found in campgrounds can scale up.

Photo supplied by owner.

Check the fridge temperatures

I would also recommend checking your refrigerator operation efficiency, meaning temperatures. Get a temperature gauge and check the inside temperature on every shelf. If your thermistor is set high on the fins, it will call for more cooling as the warm air rises. So you might need to lower it and maybe get another fan to circulate air in the cabinet.

Don’t use tin foil to line the shelves, and limit the number of canned goods in the refrigerator as they can cause more condensation. And put a 5-lb. bag of ice in the freezer. It helps with the first stage of cooling, which helps with the second stage.

You stated that it’s being operated on 120-volt power only. However, I do not believe it would make any difference on LP power. Check your door seals, temperature readings, and ambient temperature in the rig. Let us know what you find.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


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Larry C
1 year ago

Re: campground hard water clogging fridge drain hose. Since water is the fridge drain comes from the melting frost and ice on the coils, there is no campground water involved so no clogging from hard water would be possible.

Terry Hennessy Jr
1 year ago

Re: your response to reader question on REFRIG icing, you FORGOT to mention icing can often be related to OPEN Containers, MENU items (a load of high moisture vegetables), and OTHER variables related to the LOCATION, (rainy weather, visiting gkids/ family= open door, getting cold drinks, etc.) THANKS

1 year ago

What’s the filter on the fridge vent? Never heard of that.

Thomas D
1 year ago

The refrigerator is working as it’s supposed to. It’s very humid in Huston. My concern is the drain. Is the hose kinked or somehow plugged?. I ‘d get a pipe cleaner. (Yes they still make them) and move it around to clean the hose. And hard water? You don’t put water down the tray do you? It comes from the air, condensates and sometimes freezes. I’ve had bugs in my drain hose. And the pipe cleaner that I mentioned is used to clean smoking (tobacco) pipes.

1 year ago

That “useless plug” is to keep bugs from crawling into the tube, NOT to plug the tube.

John Goodell
1 year ago

Houston is bayou country, definitely not ‘dry heat’. Wet, humid, swamps, alligators. Not like Nevada.

Bob p
1 year ago

I’m not saying it’s happening but in that environment they may be opening the fridge to get cold drinks more often than at home.

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