Dear Dave,
My question is about refrigerator fans. The RV’s fridge, gas-electric, works good and always has. I put an extra fan above the top of the fridge outside to help. I would like to put one inside for better air circulation. I’ve had the battery ones but would like to have one that hooks up once to a 12-volt power source and not have to think about it. Any suggestions? —Alan, 2018 Winnebago 29VE
Dear Alan,
I have had several readers submit questions regarding addition of the external fans to help circulate air inside the unit but have always gone with the small blue model that runs on two D-size batteries. I have never had a question about how long these batteries will last, so it was a good opportunity to do some research.
Initially, I thought these ran on a 9-volt battery, back in the old days, but found all the brands on the market today are D size. It makes sense as I could not find any technical information on any of the 9-volt brands I have in the drawer, just high energy and long lasting, but what does that mean? I know that most 9-volt batteries will last at least a year in smoke alarms; however, they are not doing a constant draw like a refrigerator fan would. I also know that every 9-volt battery I have in multimeters and infrared thermometers last just up to the second I need them!
Battery ratings
According to several websites that I came across, it looks like the 9-volt alkaline battery has a milliampere-hour (mAh) rating of 550 mAh. A D-size battery is rated at 1.5 volts. That is deceiving, as it has a rating of 10,000 mAh, so two would be 20,000 mAh! However, I cannot find any technical information on what draw this fan has other than it delivers .702 CFM, and the two batteries will last 30 days, according to the Valterra website. These can’t be the same batteries that go dead the minute I pull the old flashlight out of my dad’s kitchen drawer!
So, if you are full-timing, it would make sense to connect to the house batteries rather than replacing two D-size batteries every month.
The initial fan that comes to mind is the 5” model that is typically used back on top of the cooling unit, as you have installed. When I searched for 12-volt refrigerator fan, I was amazed at how many choices there are. Most are designed to cool computers and are very inexpensive. It is also hard to get specifications. However, I did see some that had an speed rating of 3500 RPM (revolutions per minute). A handful stated they provided 6-10 CFM (cubic feet per minute)—which might be a little high and would blow your cans of beer over! But I like the fact that you can stand them up or even zip tie them to a shelf rack underneath.
Where to get power?
You will need a 12-volt positive and negative source to connect the two wires to. If your refrigerator has an interior light, you can tap in before the switch, as it will have continuous power there. Another option would be to run the wires down the drain hose hole that is typically located under the coils inside the refrigerator.
This will allow you to tap into power at the back of the refrigerator.
Frost Guard
Another option would be to look at the two or three fan products available from RV Cooling Unit warehouse that clips onto the evaporator coils and is also powered by 12-volt DC. You can find them on Amazon here.
They come with a one-year warranty and some even have an LED light.
You might also enjoy this from Dave
My RV’s refrigerator outside fans are not working. Why not?
Dear Dave,
The outside fans for my RV’s refrigerator stopped working. Why? —Ray, 2021 Palomino Columbus fifth wheel
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
Read more from Dave here.
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There are small 12 volt squirrel cage fans available. They are less that 2 inches square and about 1/2 inch deep. Easily mounted with double faced tape.
https://www.amazon.com/GDSTIME-Bearing-Brushless-Cooling-Accessory/dp/B08T189FX2/ref=sr_1_1_sspa?keywords=12+volt+fan+squirrel&qid=1701785388&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1
I installed these fans with the double stick tape and hooked up to the light power. They work great and help cool the unit more evenly and more efficiently. But they are a bit noisy and can be heard everywhere in the RV. There may be some quieter ones available.
We live seasonally stationary in our RV. The first year I had to defrost the refrigerator fins twice before the end of the 6-month season. I installed this fan unit the second winter. It is still in use 5 years later and the only defrost is at the end of the season. And there is far less ice than any of the defrosts in that first winter. Plus an IR gun shows the refrigerator is much more evenly cooled.
I would recommend placing a switch at the fan. Otherwise it will run continuously and be another saprophytic drain on the batteries when the RV is not in service.
I used the three fan one Dave mentioned. I had it off because the weather was mild outside. I noticed the fins frosted over after a week on the road. Turned one fan on and the frost disappeared. Highly recommend.
Thank you, Dave! We don’t have a lack of circulation in our refrigerator. However, our chassis mechanic is working on a solution for an excessively hot engine bay that may be solved by installing 12v fans on the inside of the hood of the engine compartment. I guess we’ll see. If we get a solution, I’ll share it with you and all the Newmar New Aire owners similarly discomfitted.