13th Oct 2026
Norcold 1200 / 1210 Flashing Temperature Setting (Thermistor Fault)
FLASHING TEMP SETTING
Norcold 1200 / 1210 Flashing Temperature Setting (Thermistor Fault)
When you press SET TEMP, your temperature setting blinks for about ten seconds instead of staying solid. It can be any setting from 1 to 9, whatever yours is set to. The thermistor (temperature sensor) reads as open or shorted, so the fridge is running on its Backup Operating System (BOS).
Before you start
- What BOS does. The fridge keeps cooling on a timed cycle instead of reading the real temperature. Raising the setting (5 to 6) runs longer cycles, and lowering it (5 to 4) runs shorter ones. Expect it to run warmer or colder than usual.
- Where it is. The thermistor clips onto the second fin from the right on the cooling fins inside the fresh-food compartment. Its wires (Red/White stripe and Red) share a plug with the interior light wires.
- You’ll need a multimeter set to kΩ and a container of crushed ice.
STEP 1
Check the display
Press the TEMP SET button and watch the number.
Is the temperature setting flashing?
Thermistor is working
The thermistor is operating as designed. If the fridge still isn’t cooling right, see other reasons for poor cooling.
STEP 2
Inspect the wires and connector
Check the thermistor wires at the thermistor itself and at its connector. Look for broken leads, and corroded or broken connector pins.
Are the wires and connections clean and in good condition?
Clean and repair the connections
Clean corrosion off the pins and repair broken wires, then press TEMP SET again. If a lead is broken at the sensor itself, replace the thermistor.
STEP 3
Do the ice test
Unplug the thermistor and unclip it from the fin. Measure its resistance at room temperature and write it down. Then put the thermistor in a small container of crushed ice and measure again.
Do the readings match the chart below (about 30–32 kΩ in ice)?
Replace the thermistor
An open reading (O.L.), zero ohms, or numbers outside the chart mean the thermistor has failed.
Norcold Thermistor 621742 →Fits the 1200 and 1210. Also sold as 636658 and 621742.The thermistor is good
Clip it back on the second fin from the right, plug it in and reset the fridge. If the setting still flashes with a good thermistor, ask a tech.
Thermistor resistance chart
Compare your room-temperature reading and your ice reading. Values are approximate.
| Temperature | Resistance |
|---|---|
| 85°F (29°C) | 8.1–9.0 kΩ |
| 80°F (27°C) | 9.1–10.0 kΩ |
| 75°F (24°C) | 10.1–11.0 kΩ |
| 70°F (21°C) | 11.1–12.0 kΩ |
| 60°F (16°C) | 12.1–13.0 kΩ |
| 50°F (10°C) | 15.5–16.5 kΩ |
| 40°F (4°C) | 22.5–23.5 kΩ |
| 35°F (2°C) | 24.5–25.5 kΩ |
| 33°F (0.5°C) | 28.5–29.5 kΩ |
| 32°F (0°C) | 30.0–32.0 kΩ |
More tips: Quickly test your Norcold thermistor.
Still stuck? ask a tech with your model, serial number and the readings you got. We’ll confirm the part before you order.
Based on the Norcold 1200/1210 service manual, Thermistor Circuit Open or Shorted (Backup Operating System) flowchart.