These sensors are also called thermistors. They’re used in lots of the recent brands to sense temperature. The old way was with a mechanical thermometer with a capillary tube. Ahh, those were the days.
The idea behind these newfangled sensors is that their resistance increases as temperature decreases. On LG refrigerators, the sensor should have a resistance 16 K-ohms ±5% at 32℉. To test the sensor:
- Measure the temperature of the sensor or the space the sensor is in. I use an infrared temperature sensing gun for this.
- Measure the sensor resistance. Make sure your meter is zero’d out and calibrated. You’re looking for readings in the k-ohms range. Note the resistance.
- Place the sensor in a glass of ice water. Let it sit for a minute or two to stabilize.
- Measure the resistance again.
You’re looking for two things:
1. That the sensor resistance did change, either up or down depending on whether you’re starting from a temperature higher or lower than 32℉. If you’re starting from a temperature higher than 32℉, then you should see the sensor resistance increase; if the starting temperature was lower than 32℉, then you should see the sensor resistance decrease.
2. The sensor resistance should be 16 ohms ±5% at 32℉.
This same procedure can be used to test any sensor in any refrigerator (many ovens use the same kind of temperature sensing technology) as long as you know the specification of the sensor at a given temperature that you can reliably produce. That’s why 32℉ is a nice test temperature to use because it’s easy and reliable to produce with ice water.
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