Traulsen Coil Sensor Open or Shorted

What does Traulsen Coil Sensor Open or Shorted mean?

This alarm indicates the controller cannot read a valid signal from the evaporator coil sensor because its circuit is open or shorted. The coil sensor is used for defrost termination and coil monitoring, so a bad reading can disrupt defrost behavior. A correct sensor reads about 32.7K ohms at 32F within ten percent.

Symptoms

• Alarm LED illuminated and horn sounding on the control
• Coil temperature reading missing or implausible
• Defrost cycles not terminating correctly
• Sensor resistance out of the expected range when tested

Common causes

• Coil sensor probe disconnected or loosely connected
• Open circuit in the coil sensor wiring
• Shorted coil sensor
• Failed coil sensor reading outside the 32.7K ohm range at 32F

Diagnostic steps

1. 01

   Locate the coil sensor

   Gain access to the coil sensor inserted on the return-air side of the evaporator coil.

2. 02

   Check the connection

   Confirm the coil sensor probe is properly connected and reconnect it if loose or disconnected.

3. 03

   Test sensor resistance

   Disconnect the sensor and place the probe in ice water; at 32F resistance should read about 32.7K ohms plus or minus ten percent.

4. 04

   Replace a failed sensor

   If resistance is outside that range, replace the coil sensor.

5. 05

   Confirm correct placement

   On freezer models center the sensor about two inches from the top through the coil; on refrigerator models mount it on top of the coil.

When to call a professional

Call a technician if reconnection does not clear the alarm or if you cannot meter the probe against the 32.7K-ohm spec. Coil-sensor placement differs between freezer and refrigerator models, and incorrect placement affects defrost termination. Accessing the evaporator coil, testing in an ice-water bath, and replacing the sensor are service tasks best handled by qualified personnel.