Norcold thermistor on wrong fin???

[azloafer]

Our Norcold fridge is too cold even at setting #1 during the winter. Somewhere on this forum I recall reading that a Norcold 1200 should have the thermistor attached to the third fin from the right. Ours is on the second fin. A close look revealed that it has never been anywhere except the second fin...no scratches on the third fin, but some on the second. The coach is a 2008 and it sure looks like the factory had it on the second fin from day one.

Fridge experts...help. Do you feel that it is on the wrong fin??? I appreciate your help. Joe

[Gary - K7GLD]

I'm certainly no "expert" - but I seriously doubt that there's any significant difference in placement of that sensor, whether it's on the second, third - or tenth fin! More important, is that it's nice and clean, and making good contact with whatever fin it IS attached to...

[Clifftall]

Quote:

Originally Posted by azloafer Our Norcold fridge is too cold even at setting #1 during the winter. Somewhere on this forum I recall reading that a Norcold 1200 should have the thermistor attached to the third fin from the right. Ours is on the second fin. A close look revealed that it has never been anywhere except the second fin...no scratches on the third fin, but some on the second. The coach is a 2008 and it sure looks like the factory had it on the second fin from day one. Fridge experts...help. Do you feel that it is on the wrong fin??? I appreciate your help. Joe

According tp Norcold, it should be on the 2nd fin.

[David K]

Maybe someone else will jump in here but, I think that the temp can be adjusted a little by moving the thermister up or down on the fin. I don't recall if going up adjusts the temp up (frig warmer) and visa versa. I am sure that someone with more knowledge than I can help with this. The second fin is the correct one for the thermister to be on. You might search this form using "thermister" as the search term and there may be more information on temp adjusting by moving it.

["007"]

Mine is on second fin 1 1/2 " from top of fin.

[Gary - K7GLD]

Quote:

Originally Posted by David K Maybe someone else will jump in here but, I think that the temp can be adjusted a little by moving the thermister up or down on the fin. I don't recall if going up adjusts the temp up (frig warmer) and visa versa. I am sure that someone with more knowledge than I can help with this. The second fin is the correct one for the thermister to be on. You might search this form using "thermister" as the search term and there may be more information on temp adjusting by moving it.

Thing is, the fin structure assembly is held in contact with the cooling coils outside the box itself with the mounting screws, using a thermo putty between the 2 surfaces to enhance cooling and transfer of heat.

IF that contact and the design of the 2 assemblies is correct, the temperature of the fins themselves should be pretty constant all across the fin assembly - only way to verify that evenness, is by a infra-red heat gun or something similar - and even at that, if a minor variation IS located, where is best for the sensor - at a lower, or higher temperature point reading on the fin assembly?

Think I'll dig out my IR temp reading gun and take a careful reading across the face of the fin structures in our 2 RV's - they're both plugged in and operating...

[SCVJeff]

Problem is that is a reflective surface and will not give you an accurate IR reading. I'm reading this late but it sure sounds like the fridge is in a fail-safe mode like the control board is in trouble. There are past threads on this.

[whem2fish]

mine is on 2nd fin as i remember move it down for warmer temp

[Gary - K7GLD]

Quote:

Originally Posted by SCVJeff Problem is that is a reflective surface and will not give you an accurate IR reading. I'm reading this late but it sure sounds like the fridge is in a fail-safe mode like the control board is in trouble. There are past threads on this.

The goal wasn't absolute accuracy in the reading, but rather, the VARIATION from fin to fin, from one end to the other as a means to determine whether there is any significant reason to be hyper over the exact fin - or where up and down that fin to place the sensor.

I suspected that in real life, it really doesn't make much difference exactly where the sensor is secured in the fin array - but most important is that it be clean and firmly attached for maximum accuracy in reading fin temps for best operation of the refrigerator.

And while it's not advised to assume that the way MY RV refrigerator fin area reads in temperature is absolutely representative of ALL refrigerators, I at least do have 2 separate ones currently in operation - the Dometic in our KIT 5er - and the Norcold in the MH - and the results are:

No more than about 2-3 degrees variation +- all over the fins on BOTH refrigerators - hardly enough on ours at least, to become paranoid over - and I suspect that the main reason refrigerator manufacturers specify the "2nd-3rd fin" location, is because the length of the lead attached to the sensor pretty well dictates that's where the sensor will physically HAVE to be secured - NOT because there's any particular "magic" in that specific location...

But yeah, my next test in that regard, will be to take readings while the unit is actually active, to see if the refrigerant flow then causes any significant variation in fin temperatures, which IF substantially different, might then make a difference. But I seriously doubt those readings will be much different than the ones I already have taken.

[powerboatr]

i can say it does matter where the thermistor is attached
when i put my new one on i used the 8th fin from the right
this has me set at temp of 3 and the box stays right at 27-30 in the bottom of the food box
if i move it to the 2 or 3rd fin it takes a setting of 5 to obtain the same temps

my fins seem to be warmer the farther left you go by 3-5 degrees using detector, does that cause the resistance to change on the thermistor? YES and according to the chart in the norcold manual and by my own testing
and i get light frost on the right fins while the left ones will be just above freezing.
hope it helps

[Ray,IN]

Thermistor has instructions for checking the thermistor. For more information try RadioShack Thermistor (271-0110)
Yahoo answers address's your problem too: My Norcold refrigerator is freezing everything! What part has failed? - Yahoo! Answers

powerboatr is right, move a good thermistor left for colder operation. For fine tuning, move it up on the same fin for cooler operation, down for warmer. Allow 24 hours between adjustments without opening door. A good wireless in/outdoor thermometer works for monitoring temperature inside a frig.

[Gary - K7GLD]

Quote:

powerboatr is right, move a good thermistor left for colder operation. For fine tuning, move it up on the same fin for cooler operation, down for warmer. Allow 24 hours between adjustments without opening door. A good wireless in/outdoor thermometer works for monitoring temperature inside a frig.

Once again, one size does NOT necessarily fit all!

As I pointed out in my earlier post, even though I personally have 2 different refrigerators to test, I'd hardly represent my measurements as representative of ALL RV refrigerators in existence - or that where I have my sensor placed is where everyone should place theirs!

If any here have actually had experience in swapping out an RV refrigerator cooling unit, or seen one up close to check out the physical mechanics and points of contact between those coils and the inner fins, you get a better picture of exactly what goes on - here's an overall pic of the failed one that came out of the Norcold unit in out MH:



The zig-zag upper section is for the freezer section of the refrigerator and is in direct contact with the rear wall of the freezer section, the lower single loop is for the refrigerator section and fin assembly that contacts the inner fins:



The clear evidence is that the coil spacing and available contact area seen varies across the face of the lower coil section, and it's not unreasonable to expect that temperature from top to bottom, and side to side would vary - especially if the original installation and application of the mastic used as an enhancement of heat transfer between the coil and fin surfaces is less than perfect.

Whether the actual real world operation of the refrigerator varies during the periods when the refrigerator is actually in it's cooling cycle remains to be seen in my own 2 refrigerators - but it sure doesn't vary much in between cycles!

I'll do another test run at a time when my refrigerator is actually in cooling mode, and get back with results...

[azloafer]

I have to take the coach in to have the dash air checked so I'll have them check the fridge too. Thanks for the helpful ideas. I'll post what they find. Thanks, Joe

[Gary - K7GLD]

I've been running some very interesting tests, and taking temperature readings - takes a while for the refrigerator to normalize after each run - will have more later...