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 > How important is a refer thermistor?

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hotjag1

Lake Chelan, Wa/Lake Havasu, Az.

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Posted: 03/29/19 06:25pm Link  |  Quote  |  Print  |  Notify Moderator

I have read on this forum that the thermistor is critical to proper refer temps because it controls the cooling cycle. Our refer starting running about 10 degrees warmer than usual(44 degrees) in 80 degree temps. I adjusted the thermistor up and down at different intervals and the temps didn't change.

After adjusting the thermistor several time the plastic clip broke off, so I just laid the broken piece with the attached wire on the shelf. After a couple of hours the refer temp went down to 37 degrees and this morning it was at 33 degrees. I changed the setting on the front of the refer down one notch and the refer stayed at about 37 degrees. So why do I need to replace the thermistor if it seems to maintain a decent temp using the front control button? It is a double door Dometic.


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PastorCharlie

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Posted: 03/29/19 06:42pm Link  |  Quote  |  Print  |  Notify Moderator

As long as it works proper do not fix it.

enblethen

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Posted: 03/29/19 07:39pm Link  |  Quote  |  Print  |  Notify Moderator

It is important for proper operation. I would use a cable tie to secure it to the rack so as not to damage it with goods in the refer. Wait for it to go bad, then replace it.
Make and model of refer? Might search for one and have knowledge on how to replace it.


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Posted: 03/29/19 09:11pm Link  |  Quote  |  Print  |  Notify Moderator

I would replace it. If it is going bad it might get worse. If you replace it you are fixing 2 problems, 1) replacing a component going bad 2) replacing a now broken component. After replacing it the fridge will be as new and everything working properly.


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Old-Biscuit

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Posted: 03/29/19 09:55pm Link  |  Quote  |  Print  |  Notify Moderator

Thermistor is the temp sensing probe that the thermostat uses to control cooling cycles (turn heat source on/off)

Thermistor senses the FIN temp and the thermostat is calibrated for the thermistors location on the OEM FIN

Adjusting the thermistor UP/DOWN is a minor temp adjustment for 'AUTO TEMP CONTROL' fridges..those that do NOT have adjustable temp settings.
Temp range is 6*-8*F overall

With thermistor NOT attached to the far right fin (OEM position) the thermostat does not have feedback on FIN temp therefore it allows continuous cooling cycle.......and is now functioning in 'limp mode'

Unplugging the thermistor from lower circuit board will have same affect


Moving 'temp setting' will have minimal affect overall.......fridge heat sources will run/operate MORE then necessary to properly cool fridge.

No need to run fridge longer then necessary.

Snip-The-Tip ....thermistor replacement w/o having to pull old leads out/run new leads ....replaces the thermistor probe with a 'rheostat' control that attaches to side wall of food compartment


OR NOT.........it's your fridge and you can do as you please.
Folks 'jury-rig' stuff all the time.


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hotjag1

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Posted: 03/29/19 10:20pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks Old Biscuit... that is a great explanation as to how the thermistor works in relation to the functions of an rv fridge. I will replace the thermistor as it is a very inexpensive part and I want the refer to operate as originally designed. If it was something that might cost several hundred dollars, I might think otherwise(jury-rig) since the refer could be used and kept cool as you state.

Thank-you for the in-depth explanation. BTW, you add a lot of very good information to this forum on many subjects!

Scottiemom

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Posted: 03/30/19 04:39am Link  |  Quote  |  Print  |  Notify Moderator

I believe the thermistor is important to defrosting the fridge. When ours was not working, the fridge was still cold, but the fins would build up with ice and couldn't melt. It also caused water droplets to build up on the roof of the case and things would be wet when we were in/out of it while fixing a meal. It was a quick easy fix to install a new one that DH did himself.

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Ralph Cramden

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Posted: 03/30/19 05:21am Link  |  Quote  |  Print  |  Notify Moderator

hotjag1 wrote:

I have read on this forum that the thermistor is critical to proper refer temps because it controls the cooling cycle. Our refer starting running about 10 degrees warmer than usual(44 degrees) in 80 degree temps. I adjusted the thermistor up and down at different intervals and the temps didn't change.


Is the fridge 10 degrees warmer than it was before when the ambient temperature was 80? or 10 degrees warmer than when the ambient temperature was 70?

An absorption fridges ultimate cooling ability is related, although not directly related in terms of a degree cooling for every degree ambient, to the ambient temperature. Once the ambient is above 80, even more so if the sun is on the side of the rig with the fridge, the fridge starts getting incapable of supporting those interior temps in the 30's no matter the thermistor position, brand, age, or anything else.

Add to that the RV manufacturers are notorious for building the compartment wrong instead of following the fridge manufacturers guidelines, so they don't naturally draft enough. That or they jam them in a slide with no ability to use a roof vent.

Adding 12 volt fans to vent the space is the cheapest and best mod one can make to any absorbtion fridge. If you have a Dometic with the OEM fan, it's a noisy POS anyway or it will be given time. If you add some good fans you can kill the OEM one.

dougrainer

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Posted: 03/30/19 06:51am Link  |  Quote  |  Print  |  Notify Moderator

Scottiemom wrote:

I believe the thermistor is important to defrosting the fridge. When ours was not working, the fridge was still cold, but the fins would build up with ice and couldn't melt. It also caused water droplets to build up on the roof of the case and things would be wet when we were in/out of it while fixing a meal. It was a quick easy fix to install a new one that DH did himself.

Dale


RV refers have NO defrost cycle at all. All RV refers do is cool the items. Frost/ice build up you must manually defrost them. IF you have excessive ICE on the evap fins, that will degrade the cooling capacity as ICE is a great insulator for cooling capacity. A thin film of ice is normal and will not degrade cooling. Doug

ppine

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Posted: 03/30/19 07:53am Link  |  Quote  |  Print  |  Notify Moderator

Important to control the temp.

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