The Thermo King alarm 05 indicates that the unit has detected an issue with the ambient temperature sensor.
Possible causes of alarm code 05 include:
- A defective or damaged ambient temperature sensor.
- A loose or disconnected connection to the ambient temperature sensor.
- An issue with the unit’s wiring.
The alarm 05 Thermo King can be identified as follows:
| Alarma 05 Thermoking | |
|---|---|
| Green = OK | Check the ambient temperature sensor. |
| Report the alarm at the end of the day. |
Cause of Fault Code 5 Thermoking:
The circuit feeding the sensor may be:
- Open circuit.
- Short circuit.
When the Thermoking system uses a PT1000-type sensor, the system module detects an open circuit problem when the resistance measurement of the sensor circuit is above 1300 Ω. The short circuit of the sensor is detected when the sensor circuit resistance is below 602 Ω.
Location of the Problem Causing Alarm 05 Thermoking:
- Defective or incorrect sensor.
- Defective wiring.
- Defective regulator.
What to Do with Alarm 05 Thermoking:
- Check for damaged sensor cables.
- Verify sensor connections to the controller.
- In some models, the sensor is a Pt1000, a two-terminal sensor that can be swapped without affecting measurement.
- Disconnect the sensor and, with a multimeter in the Ω position, measure the electrical resistance between the two sensor cables.
- The sensor cannot be examined without disconnecting it.
- When the sensor is a Pt1000, it has a positive temperature coefficient. This means that the sensor’s electrical resistance increases with temperature.
- The sensor is calibrated to have a resistance of 1,000 Ω at 0 °C.
- Normal resistance values with the PT1000 sensor can be seen in the following table:
| -10 °C | 960 Ω |
| 0 °C | 1,000 Ω |
| +10 °C | 1,039 Ω |
| +15 °C | 1,058 Ω |
| +20 °C | 1,078 Ω |
| +75 °C | 1,300 Ω |