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Old 04-18-2012, 11:04 PM   #1
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Dometic fridge freezing food

I've tried adjusting the thermistor slide down the first fin as low as it will go, but it still freezes the every thing.
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Old 04-19-2012, 04:12 AM   #2
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Check for good clean and tight fitting connection of thermistor to control board. If this is OK, then a diagnosis of the thermistor resistance to temperature is needed. If it is OK you could have a bad (stuck) relay on the control board. Good luck, stay safe and keep us posted.
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Old 04-19-2012, 08:32 AM   #3
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Where do I find this control board, thru the opening outside? Will I need to take this to an RV tech to check this resistance and check the relay?
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Old 04-19-2012, 08:48 AM   #4
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If your thermistor is bad it will not shut the refrigerator down once it gets to the temperature that you have it set for, the refrigerator will keep running. Make sure that the mounting point is clean and it is making a good contact to your fins. You can check your thermistor with a ohm meter by placing it into a container of ice and take a reading, it should be around 76 ohms I believe. RV Wizard can correct me if I'm wrong.
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Old 04-20-2012, 03:33 AM   #5
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Dometic Thermistor: To test the Dometic thermistor, disconnect it from the main (lower outside access vent area) circuit board and place the other end (sensor end) into a glass of ice water. After a few minutes you should be able to get a resistance reading of 7,000 to 10,000 ohms between the two terminals of the connector. If the resistance isn't close to those numbers, it is bad.
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Old 04-20-2012, 03:41 AM   #6
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Quote:
Originally Posted by RV Wizard View Post
Dometic Thermistor: To test the Dometic thermistor, disconnect it from the main (lower outside access vent area) circuit board and place the other end (sensor end) into a glass of ice water. After a few minutes you should be able to get a resistance reading of 7,000 to 10,000 ohms between the two terminals of the connector. If the resistance isn't close to those numbers, it is bad.
Thanks Mike, It's been way to long, just a senior moment.
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Old 04-21-2012, 04:04 AM   #7
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Hey Bruce, no problem. I had to look it up to be sure myself.
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Old 04-21-2012, 03:33 PM   #8
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I checked the thermistor, and with my ohm meter set to RX1K, I got a reading of 5. That seems too low. Replace thermistor wire? That should be fun, but, I'm sure, better than a relay.
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Old 04-21-2012, 04:26 PM   #9
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I just rechecked the thermistor resistance after a longer period in ice water and now it reads 8.
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Old 04-21-2012, 04:56 PM   #10
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What model is the Dometic? I would try the thermistor on the 3rd or 4th fin-first fin might not get as cold as the others.
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Old 05-11-2012, 10:05 PM   #11
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Thermistor Problem - Fridge freezes everything

I have a Dometic RM2652 and had problems with the thermistor. I followed the directions for testing the thermistor just like everyone suggested (ice water bath and check for resistance of between 7000 and 10000 ohms) which indicated that the thermistor was fine (approx 8500 ohms). This lead me to believe that the control board was the problem since I had no problem with the fridge producing cold. I replaced the board with a standard control board which should have fixed the problem but to my surprise the fridge still wouldn't shut off. The only logical thing left was to assume that somehow something was wrong with the thermistor. THIS is the important part: I took a decade resistance box and connected it to the port were the thermistor plugged in. I preset the resistance to 10k ohms and guess what... the fridge remained OFF. I then slowly lowered the resistance (100 ohm steps) until it hit 9k ohms and the refrigeration turned ON. I then increased the resistance (again in 100 ohm steps) and when 9.8k ohms was reached the fridge turned OFF. I tried lowering and raising the resistance to confirm that the operation was not just a fluke. I then took a new replacement thermistor and put it in ice water for 5 minutes and checked the resistance. It was only 9.5k ohms. A brand new thermistor and it would never work. What to do now? Well, I decided what I needed to do was to increase the resistance of my new thermistor. To make this part brief, what I ended up doing was adding in a 2k ohm potentiometer to one of the wires connected to the thermistor which allows me to now put the thermistor is an ice bath and tweak the resistance to approximately 10k ohms. My fridge is now working perfectly and keeps a steady 3 degrees celcius. I now also have the added benefit of being able to adjust my temperature with greater control. Please keep in mind that the resistive values I discovered may or may not work for all boards but if you have problems and follow the methadology of my testing it might help you out. If anyone wants a picture of the circuit just drop me an email and I'll send it off to you.
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Old 05-11-2012, 10:47 PM   #12
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Some models have a thermistor control on the circuit board. If you don't have one and want one, contact tvformyrv.com
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Old 05-13-2012, 09:06 AM   #13
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Quote:
Originally Posted by Don the tech View Post
I have a Dometic RM2652 and had problems with the thermistor. I followed the directions for testing the thermistor just like everyone suggested (ice water bath and check for resistance of between 7000 and 10000 ohms) which indicated that the thermistor was fine (approx 8500 ohms). This lead me to believe that the control board was the problem since I had no problem with the fridge producing cold. I replaced the board with a standard control board which should have fixed the problem but to my surprise the fridge still wouldn't shut off. The only logical thing left was to assume that somehow something was wrong with the thermistor. THIS is the important part: I took a decade resistance box and connected it to the port were the thermistor plugged in. I preset the resistance to 10k ohms and guess what... the fridge remained OFF. I then slowly lowered the resistance (100 ohm steps) until it hit 9k ohms and the refrigeration turned ON. I then increased the resistance (again in 100 ohm steps) and when 9.8k ohms was reached the fridge turned OFF. I tried lowering and raising the resistance to confirm that the operation was not just a fluke. I then took a new replacement thermistor and put it in ice water for 5 minutes and checked the resistance. It was only 9.5k ohms. A brand new thermistor and it would never work. What to do now? Well, I decided what I needed to do was to increase the resistance of my new thermistor. To make this part brief, what I ended up doing was adding in a 2k ohm potentiometer to one of the wires connected to the thermistor which allows me to now put the thermistor is an ice bath and tweak the resistance to approximately 10k ohms. My fridge is now working perfectly and keeps a steady 3 degrees celcius. I now also have the added benefit of being able to adjust my temperature with greater control. Please keep in mind that the resistive values I discovered may or may not work for all boards but if you have problems and follow the methadology of my testing it might help you out. If anyone wants a picture of the circuit just drop me an email and I'll send it off to you.


Good post! Thanks for the advice and for joining IRV2.
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