Kolpak Walk-In Cooler Alarm AIR TEMP SENSOR: Return Air Probe
AIR TEMP SENSOR on a Kolpak walk-in's ArcticFox controller means the return air temperature sensor is shorted or open. Press ENTER to silence the alarm for 1 hour. The controller uses this sensor for room temperature, so check the room yourself and call service.
High: this is the sensor behind room temperature, so the walk-in could drift without a trustworthy reading.
- Code
- AIR TEMP SENSOR
- Maker
- Kolpak
- Equipment
- Walk-in coolers & freezers
- Applies to
- ArcticFox OEM Controller with Deluxe Display (Kolpak walk-ins)
What does Kolpak AIR TEMP SENSOR mean?
The return air sensor tells the ArcticFox controller how warm the walk-in is. It is the reading used to decide when to cool and when the room is outside its limits. If the sensor is shorted or open, the controller loses that reading and raises the text alarm AIR TEMP SENSOR in the Alarms menu. The manual's definition is a return air temperature sensor that is shorted or open, and its action is to press ENTER to silence the alarm for 1 hour while the condition is addressed. The alarm sounds again if it has not been corrected. The manual lists no other causes. Because this is the sensor behind the room temperature, a bad reading can hide a real problem or invent one, and the HIGH AIR TEMP and LOW AIR TEMP alarms depend on the same measurement. A separate thermometer in the box is the only dependable check until the sensor is repaired.
Affected models and control systems
The manual covers the ArcticFox OEM Controller with Deluxe Display used on Kolpak walk-in coolers and freezers.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- AIR TEMP SENSOR in the Alarms menu
- Room temperature display showing an odd or fixed value
- Alarm sounding again after an hour
- Compressor running much longer or shorter than usual
Possible causes
Likely causes — what usually sits behind AIR TEMP SENSOR on this control. A technician confirms which one it is before any part is replaced.
- Return air temperature sensor shorted
- Return air temperature sensor open
- Sensor cable damaged by pallet jacks or product movement near the evaporator
- Probe wet or iced after a door left open
- Connector loose at the controller or at the evaporator housing
Safe checks before calling for service
- Press ENTER on the display to silence the alarm for 1 hour.
- Place a thermometer in the room and check that the temperature is holding.
- Look for product or objects pushed against the evaporator housing where the sensor lead runs.
- Keep the door closed as much as possible.
- Call for service and describe both the alarm text and the thermometer reading.
How a technician diagnoses AIR TEMP SENSOR
- Read the Alarms menu and the room temperature shown by the controller.
- Compare the displayed temperature with a reference thermometer.
- Inspect the sensor and cable path near the evaporator.
- Measure the sensor resistance and check the connector at the controller.
- Replace a sensor that is open or shorted and check the room temperature reading.
- Confirm HIGH AIR TEMP and LOW AIR TEMP alarms are not triggered by a wrong reading.
- The sensor sits by the evaporator, where a technician works around fans and live wiring.
- A technician has to match the sensor's resistance to temperature with a meter and chart.
- Replacing the sensor changes what the controller sees, so the room's temperature has to be verified afterward.
How AIR TEMP SENSOR differs from similar codes
AIR TEMP SENSOR is the return air probe. COIL TEMP SENSOR is the evaporator coil probe, and they are separate alarms.
Technical reference
- Document
- ArcticFox Deluxe Display - Original Instructions, Installation, Operation and Maintenance Manual
- Edition
- Part No. 500002385-4, 5/23
- Models / control
- ArcticFox OEM Controller with Deluxe Display (Kolpak walk-ins)
- Section
- ArcticFox OEM Controller - Alarms Menu, p.16
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Kolpak walk-in cooler & freezer error codes
Can I rely on the temperature display?
Not while this alarm is active. Use a separate thermometer.
Why might HIGH AIR TEMP show up too?
The air alarms rely on the same room reading, so a bad sensor can confuse them.
How do I silence the alarm?
Press ENTER on the display. The manual says it stays silent for 1 hour.
Need help with Kolpak AIR TEMP SENSOR?
A technician confirms the cause on site and gives you the price in writing before any work starts.