Norcold RV Fridge Thermistor Testing & Repair Guide

This page teaches how to test and fix Norcold RV fridge internal temperature sensor (thermistor) problems.

Table of Contents

Norcold fridge not cooling?

Diagnosing and repairing thermistors including wiring and measuring the refrigerator cabinet temperature sensor before replacing a perfectly good sensor.

We include this video on this page to teach how to:

  • Remove thermistor wire from controller
  • Show that the fridge will run full time with thermistor disconnected
  • Compare fridge temperature to actual temperature in fridge
  • Check thermistor location
  • Check thermistor plug
  • Check wire from control to sensor
  • Thermistor changing resistance
💡 For those that like written instruction with details – please read on 😁

Thermistor Troubleshooting

The first and easiest thing to check is the location of the thermistor within the refrigerated cabinet. Use the photos below to find the location of the thermistor for your fridge model. Next we will discuss two simple ways to test the function of your refrigerator thermistor:

1) Use a thermometer in the fridge and compare the temperate to the temperature read out on the Norcold control panel while in the diagnostics mode. If the temperatures are similar, then the thermistor is working. Also, a remote fridge & freezer thermometer can be used like in the video above. Use the thermistor tables below to determine if the thermistor is working.

2) Use the chart below to get two resistors. One resistor will be the warm resistor (10k?) and one the cold resistor (30k?). Simply test to see if the fridge turns on and off with these two resistors. Use the warm resistor to run the fridge 100% of the time while measuring the cabinet temperature. This method should help narrow the problem down to being the thermistor or not. Also, when the thermistor is disconnected from the fridge controller, the fridge will run 100% of the time, as a result, if the food in your fridge is freezing the thermistor may need to be checked for being open.

Next, if you think that the thermistor is failing, please note that there are two wires on the thermistor. On some refrigerators they go to a connector that also supplies power to the interior lamp for the fridge. Disconnect the connector and measure the resistance of the thermistor according to the table below. Please note that the table below is a copy of the Norcold 1200 repair manual. For your convenience see the table at the bottom of this page. You can pull the thermistor off and put it into your freezer, and then check it at the temperature in your RV. Please note, what you want to see is a change of resistance for the thermistor, not the exact reading in the table below.

Rusted or Corroded Terminals

3 Connector Troubleshooting) Please note in the 2nd image below, the thermistor has a connector (red arrow) within the fridge compartment. Look carefully at the thermistor terminal connections within this connector, often the connector thermals rust. This results in high resistance at the terminal; this can be the entire problem! We suggest cutting the wire off the connector and replacing the connector terminals with your own, then pack the terminals with silicon grease to prevent corrosion.

Thermistor Norcold 1200, 1201, 1210, 1211, 2118 Series

The proper location for the thermostat or thermistor in Norcold 1200, 1210 & 2118 series RV refrigerators.

This photo is a Norcold 1200 or 1210 Series thermistor attached in the proper position on the cooling fins. If the Norcold refrigerator thermistor is attached on the wrong cooling fin, the fridge will appear to not cool correctly. Please start by checking that your thermistor is located properly.

Norcold Thermistor N7x & N8x Series

The proper location for the thermostat or thermistor in Norcold N7x, N8x, or N10x RV refrigerators.

This photo is a Norcold N7x & N8x thermistor in its proper location. Note that the thermistor is on the 10th cooling fin from the right of the fridge. Read the next section for testing.

Norcold Thermistor 620, 621, 641, 811, 820, 821, 841 Series

Norcold 6xx, 8xx series thermistor location with identifying arrows to show the thermistor connector & location.

This photo is a Norcold N611/N641 thermistor in its proper location. Note that the thermistor is connected to a quick connector (red arrow). the yellow arrow points to the thermistor on the proper cooling fin. The blue arrow points to wiring that we added so that we could test this thermistor with a data collection Fridge Defend control. Another method to repair the thermistor, just take it off the cooling fin and allow it to dangle in the fridge. This will keep the thermistor from cooling on the fin and could show a thermistor that the ohms at a given temperature shifted (drift) from its proper value, thus preventing the fridge from turning on.

Norcold Thermistor 3104 & 3150 and 4104 & 4150 Series

The proper location for the thermistor for the N3104 and N3150 is on the 5th fin from the right on the cooling fins at the back of the refrigerated cabinet.

Norcold Thermistor 1095 Series

Proper location for the thermistor is on the 10th fin on the cooling fins at the back of the refrigerated cabinet.

Norcold Thermistor N510 Series

Proper location for the thermistor is on the 5th fin on the cooling fins at the back of the refrigerated cabinet.

Norcold Thermistor Error Codes

Model Error Meaning
2118 Flash When viewing cabinet temperature LED flash.
2117 C1 Refrigerator thermistor out of range.
2117 C2 Freezer thermistor out of range.
N3104 13.00 Failed thermistor.
N3150 13.00 Failed thermistor.
1200 Flash When viewing cabinet temperature LED flash.
1201 Flash When viewing cabinet temperature LED flash.
1210 Flash When viewing cabinet temperature LED flash.
1211 Flash When viewing cabinet temperature LED flash.
N1095 Flash When viewing cabinet temperature LED flash.
N510 Flash When viewing cabinet temperature LED flash.
N501.3 Note 1
N501 Note 1
N500 Note 1
N401.3 Note 1
N401 Note 1
N400 Note 1
N306 Note 1
N305 Note 1

NOTES

Note 1: Capillary Tube Type Sensor

Norcold Thermistor Calculated Table

Following table is for Norcold Models:

2117 | 1200 | 2101 | 1210 | 1211 | N3104 | N3150 | N1095 | N811 | N820 | N821 | N841 | N611 | N620 | N621 | N641 | N510

The following tables are calculated values based on the information provided by Norcold. The values are presumed to be correct based on standard thermistor construction. At a given temperature the resistance is given if everything was perfect (Calculated ?). More importantly, the actual range of resistance should be between Range Low Ohm and Range High Ohm, but may still differ from these values somewhat because as thermistors age they drift. Norcold states that these values may be +/- 10% above and below the table values.

Temperature (degF) Temperature (degC) Calculated (Ohm) Range Low (Ohm) Range High (Ohm)
-8 -22.22 109675 102023 117328
-7 -21.67 106164 98786 113542
-6 -21.11 102777 95662 109892
-5 -20.56 99510 92649 106371
-4 -20.00 96358 89740 102976
-3 -19.44 93317 86933 99701
-2 -18.89 90382 84224 96541
-1 -18.33 87550 81608 93492
0 -17.78 84817 79083 90550
1 -17.22 82178 76644 87711
2 -16.67 79630 74289 84971
3 -16.11 77170 72015 82326
4 -15.56 74795 69818 79772
5 -15.00 72500 67695 77306
6 -14.44 70284 65644 74925
7 -13.89 68144 63662 72625
8 -13.33 66075 61747 70404
9 -12.78 64077 59896 68258
10 -12.22 62146 58107 66185
11 -11.67 60280 56377 64182
12 -11.11 58476 54705 62246
13 -10.56 56732 53088 60376
14 -10.00 55046 51524 58568
15 -9.44 53416 50012 56820
16 -8.89 51839 48549 55130
17 -8.33 50315 47134 53496
18 -7.78 48840 45765 51916
19 -7.22 47414 44440 50389
20 -6.67 46034 43158 48911
21 -6.11 44699 41917 47481
22 -5.56 43407 40716 46098
23 -5.00 42157 39554 44760
24 -4.44 40947 38428 43466
25 -3.89 39776 37338 42213
26 -3.33 38642 36283 41000
27 -2.78 37544 35262 39827
28 -2.22 36481 34272 38690
29 -1.67 35452 33313 37590
30 -1.11 34455 32385 36525
31 -0.56 33489 31485 35494
32 0.00 32554 30613 34495
33 0.56 31648 29769 33528
34 1.11 30770 28950 32590
35 1.67 29920 28157 31683
36 2.22 29095 27388 30803
37 2.78 28297 26642 29951
38 3.33 27522 25920 29125
39 3.89 26772 25219 28325
40 4.44 26044 24539 27549
41 5.00 25339 23880 26797
42 5.56 24654 23241 26068
43 6.11 23991 22621 25361
44 6.67 23348 22020 24676
45 7.22 22724 21436 24011
46 7.78 22118 20870 23367
47 8.33 21531 20321 22742

Norcold 2118 PolarMax Thermistor Table

Temperature (F) Temperature (C) Approximate Resistance (kOhms)
32 0.0 30 - 32
33 0.6 28.5 - 29.5
35 1.7 24.5 - 25.5
40 4.4 22.5 - 23.5
50 10.0 15.5 - 16.5
60 15.6 12.1 - 13
75 23.9 10.1 - 11
80 26.7 9.1 - 10
85 29.4 8.1 - 9