Reefer Temperature Sensor Failures: Symptoms, Diagnosis and Replacement

Reefer temperature sensors are essential for maintaining proper temperature control in refrigerated containers. A faulty sensor can cause incorrect readings, controller alarms and unstable refrigeration system performance.

Detecting the problem early is key to avoiding cargo damage, reducing downtime and preventing more expensive repairs.

In this guide, we explain how to identify reefer temperature sensor failures, the most common symptoms, how to diagnose the issue and when replacement is necessary.

Common symptoms of reefer temperature sensor failures

Temperature sensors can fail due to wear, moisture, vibration or wiring issues.

The most common symptoms include:

• Incorrect temperature readings: the controller displays values that do not match the actual temperature inside the container.
• Recurring alarms: the unit may trigger alarms related to temperature deviation or sensor failure.
• Unstable refrigeration cycles: the compressor starts and stops irregularly.
• Abnormal defrost cycles: the system may activate unnecessary defrost cycles or fail to run them correctly.

If you notice these issues, check our category of reefer temperature sensors.

Most common causes of failure

Sensor failures are not always caused by the sensor itself. It is important to identify the real source of the problem.

The most frequent causes are:

• Moisture and corrosion: sensors work in harsh environments and may deteriorate over time.
• Wiring damage: cables may become worn, broken or disconnected.
• Normal wear: over time, a sensor can lose accuracy.
• Faulty connections: poor electrical contact may result in erratic readings.

How to diagnose a faulty reefer temperature sensor

Before replacing the sensor, it is advisable to confirm that it is actually defective.

Basic diagnostic steps:

1. Check the alarm code: the controller often indicates which sensor is affected.
2. Compare actual temperature vs displayed reading: use an external thermometer to validate the value shown.
3. Inspect the sensor physically: look for visible damage on the cable or connector.
4. Measure electrical resistance: if you have the proper tools, check whether the sensor values are consistent.

If you need help finding the correct replacement, see our guide on how to identify the correct part code on your reefer container.

When should you replace a reefer temperature sensor?

You should replace the sensor when:

• The temperature readings are clearly incorrect.
• The issue remains after checking the wiring.
• The sensor shows visible physical damage.
• The unit continues to trigger alarms.

In these cases, the most effective solution is to install a new compatible replacement.

Browse available options in our category of temperature sensors for reefer containers.

Sensors used in Carrier, Thermo King, Daikin and Star Cool units

Each manufacturer uses specific sensor references, although the function is essentially the same: monitoring temperature accurately and transmitting data to the controller.

Carrier

Carrier reefer units commonly use thermistor-based sensors connected to the control system.

See compatible parts in Carrier reefer spare parts.

Thermo King

Thermo King units rely on supply and return air sensors for precise temperature management.

See compatible parts in Thermo King reefer spare parts.

Daikin

Daikin reefer systems integrate multiple sensors to improve system performance and temperature regulation.

See compatible parts in Daikin reefer spare parts.

Star Cool

Star Cool units use temperature sensors to maintain stable operating conditions and improve refrigeration control.

See compatible parts in Star Cool reefer spare parts.

How to replace a reefer temperature sensor

Replacing a reefer temperature sensor is usually a straightforward task for qualified technicians.

Basic steps:

1. Disconnect the unit from power.
2. Locate the faulty sensor.
3. Disconnect the old sensor.
4. Install the new sensor.
5. Secure the cable properly.
6. Check the unit and confirm correct operation.

After replacement, make sure that:

• No alarms remain active.
• The temperature readings are stable.
• The refrigeration system operates correctly.

Where to buy reefer temperature sensors

Using the correct replacement sensor is essential to avoid repeated failures and ensure proper refrigeration performance.

At Depot, you can find temperature sensors compatible with:

• Carrier
• Thermo King
• Daikin
• Star Cool

Explore our selection of reefer temperature sensors.

Frequently asked questions about reefer temperature sensors

What happens if a reefer temperature sensor gives incorrect readings?

It can cause overcooling, cargo damage, repeated alarms or incorrect refrigeration system performance.

How often should reefer temperature sensors be replaced?

There is no fixed replacement interval. They should be checked during preventive maintenance and replaced when they show inaccurate readings, visible damage or electrical faults.

Can I install any sensor in a reefer unit?

No. The replacement sensor must be compatible with the brand, model and part reference of the unit. Using the wrong sensor may lead to incorrect readings and system malfunctions.

Conclusion

Reefer temperature sensor failures are one of the most common causes of refrigeration issues in refrigerated containers.

Identifying the fault early and installing the correct replacement helps prevent major breakdowns, protect the cargo and keep the reefer unit operating efficiently.

If you notice abnormal temperature readings or repeated alarms, checking the sensor should always be one of the first diagnostic steps.