How Your RV Refrigerator Thermistor Works -- My RV Works

My RV Works, Inc., RV Technician, Darren Koepp, briefly discusses a question from a Livestream episode about the functionality of the Thermistor in RV refrigerators. Watch to learn how the thermistor works and how to change the temperature of your RV refrigerator by adjusting the thermistor position.
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Topic: Thermistors
System: RV Refrigerators
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[@jimjessup3979]

Knowing HOW something works provides a foundation for knowing how to make something work correctly. Thank you for explaining the details for the "equipment of the day."

[@hillbillyrv]

Good explanation Darren

[@billyskullz]

So Todd from NRVTA just mentioned you, I had a feeling you went here, stated you are an " an engineer", lol. Sitting in class as I write this at nrvta. Cheers myrvworks.

[@torlofske5279]

Excellent explanation. I've wondered for some time exactly how the thermistor functioned. Thank you!

[@richardzelesket4869]

Put it in and tryed it on different days all settings worked as should .Gas, Elect , and 12 volt.

[@DragonPilot]

Which way should you slide the thermistor to set a cooler temp?

[@MyRVWorks]

On a Dometic refrigerator, if you have that white clip with a thermistor in it, it is typically located on the right side fin. But note that different Dometic models do move the thermistor to different sides. But if you slide it up, the refrigerator will tend to run a little bit cooler, if you slide it down, the refrigerator will tend to run a little bit warmer. We also put out a video that talks about the relationship between the thermistor and the 'number' settings. Here's a link to it: kzbin.info/www/bejne/mIqalKxqgMtmjLMsi=kJf2kzgvsDQRALlu

[@DragonPilot]

@@MyRVWorks Thanks. My thermistor on my Dometic 8501 looks like a small flat square tile on the left-most fin. The wire going to it, which I assume is a temp probe, has no slack in it preventing me from moving up what I think is the thermistor. Wish I could attach a pic. Maybe on your website.

[@diverm2371]

Thanks Keep more coming please

[@MyRVWorks]

We will!

[@kmisercola7180]

So I have a rm2611 that I had working real good last summer by getting good air flow in the exterior compartment. This year the freezer is 8 -12 degrees but I can't get the fridge into the 30's at all one thermistor would run around 49 degrees and the other would run around 41. What am I missing or are both of my thermistors junk?

[@jerryplante4239]

The way I remember it. The thermostat (the slide switch that says cool and cooler) turns the colling unit on, the thermistors turns it off.

[@MyRVWorks]

In this video we discussed the relationship between a thermistor and the cool setting numbers. kzbin.info/www/bejne/mIqalKxqgMtmjLMsi=kJf2kzgvsDQRALlu

[@Nomujy4u]

My 2 way Dometic fridge used to work good until recently. I've replaced my thermistor but yet the fridge doesn't get cold enough even with the thermistor as high up as I can put it. (Propane and Electric) I've burped the fridge and there are no signs of Ammonia leak. The trailer is perfectly level and I live at sea level. The freezer gets Ice cold no problems. I'm at my wits end to some degree. Do I need to replace the control board?

[@chriscatron3864]

What do you mean you “burped” the fridge? Did you check the Ohms reading on the Thermistor? Are you sure it was bad? Are you getting any codes on the display?

[@chriscatron3864]

Have you checked your door seals. If you put a dollar bill on the seal, you should not be able to easily pull it out with the door shut. If you can the seals are bad.

[@rjapcok]

On a Dometic, does moving the thermistor up cause it to get colder?

[@MyRVWorks]

In a properly operating refrigerator, yes you are correct, sliding the thermistor up would cause the refrigerator to run a little cooler. Here's a video we did where we talk about the relationship between the thermistor and the cool setting numbers. kzbin.info/www/bejne/mIqalKxqgMtmjLMsi=kJf2kzgvsDQRALlu

[@Pack.Leader]

I just de-iced my fins yesterday. I have a Norcold. You said the thermistor should be on the 10th fin from the right. I just went and counted and it's on the 11th. Does that really matter? I made the mistake of removing the thermistor in my first motorhome when defrosting it, not knowing that it actually matters what fin it's clipped to. I hesitate to mess with them now but if it should be on the 10th fin, I will move it over. Also, you mentioned moving the thermistor up and down on the fin, but you didn't say why that matters or when you should adjust that. Thank you very much. I've already got frost coming back on the fins nearest to the thermistor. That didn't take long ! (Wouldn't it be great if they would put a mark on the fin to show us all where the thermistor belongs????)

[@MyRVWorks]

Norcold and Dometic approach thermistor location and adjustment differently. Also, not all refrigerators place thermistors in the same locations. So these are just general guidelines without knowing specifics. For your Norcold, it starts on the 10th fin from the right. Then if your refrigerator is running too warm or too cold you move it either to the left or the right a fin until you achieve the desired temperature. On a Dometic, you raise it and lower it to achieve the desired temperature. If your refrigerator was operating within correct temperature (which is 37° to 40°F). Then by all means leave it on the 11th fin. At some point maybe it was adjusted there to achieve that temperature. One thing you might want to check is the drain tube that leaves the bottom drip tray and works its way outside to near your boiler. Typically that is a white PVC tube , and it should have an insect screen plugged into the end of it. If that is open to the air, you have a air breach directly into your food compartment and that may be contributing to the frost buildup. A best practice is practice is to bend that tube into a bit of a P-trap to help block air but still allow it to drain water out.

[@Pack.Leader]

@@MyRVWorks Alright. Thank you very much. Great info and advice.

[@Yukonjackman1]

You didn't say up colder towards the top, or warmer towards the top im guessing cooling better moved up the fin in a dometic frig

[@MyRVWorks]

Sorry about that, yes, typically if the refrigerator is working correctly, sliding the thermistor up will allow it to run a little cooler. Here's a video we put out a while back talking about the relationship between the thermistor and the cool setting numbers. kzbin.info/www/bejne/mIqalKxqgMtmjLMsi=kJf2kzgvsDQRALlu