Kolpak Walk-In Cooler Alarm COIL TEMP SENSOR: Evaporator Probe
COIL TEMP SENSOR on a Kolpak walk-in's ArcticFox controller means the coil temperature sensor is shorted or open. Press ENTER to silence the alarm for 1 hour. The alarm returns if the condition is not corrected.
Medium: the controller has lost the evaporator reading, and the room may still cool for a time.
- Code
- COIL TEMP SENSOR
- Maker
- Kolpak
- Equipment
- Walk-in coolers & freezers
- Applies to
- ArcticFox OEM Controller with Deluxe Display (Kolpak walk-ins)
What does Kolpak COIL TEMP SENSOR mean?
The coil sensor measures the temperature of the evaporator. A controller uses it to see how cold the coil is, which matters for managing defrost. When the ArcticFox controller finds this sensor shorted or open, it shows the text alarm COIL TEMP SENSOR in the Alarms menu. The manual defines the alarm as a coil temperature sensor that is shorted or open and gives one action, which is to press ENTER to silence it for 1 hour while the condition is addressed. If the problem is not corrected in that hour, the alarm sounds again. It lists no further causes and does not describe what the controller does without the coil reading, so we do not claim that defrost stops or runs long. In practice, a coil probe that is lost is something to repair before heavy frost builds up on the evaporator, since you cannot see the coil in operation.
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
- COIL TEMP SENSOR in the Alarms menu
- Alarm repeating after being silenced
- Frost visible on the evaporator or ice on the fan guard
- Longer or more frequent defrosts
Possible causes
Likely causes — what usually sits behind COIL TEMP SENSOR on this control. A technician confirms which one it is before any part is replaced.
- Coil temperature sensor shorted
- Coil temperature sensor open
- Sensor lead damaged during defrost heating or ice removal
- Probe displaced from the coil fins
- Moisture or ice on the connector at the evaporator
Safe checks before calling for service
- Press ENTER on the display to silence the alarm for 1 hour.
- Check room temperature with a thermometer and look at the evaporator from outside the housing.
- Do not chip ice or move the sensor lead.
- Note whether the defrost cycle has been running normally.
- Call for service and give the alarm text and what you saw.
How a technician diagnoses COIL TEMP SENSOR
- Read the Alarms menu and the coil temperature on the controller.
- Inspect the probe position on the coil and trace its lead.
- Measure the probe's resistance and compare it with the actual coil temperature.
- Check the connector and the controller input.
- Replace the probe if it is open or shorted, and secure it where the manufacturer specifies.
- Run a defrost and watch the coil reading respond.
- The coil probe is on the evaporator, which has fans and defrost heaters carrying live voltage.
- Ice on the coil has to be removed and the area dried before the lead can be inspected.
- Placing the probe correctly on the coil affects defrost, so it has to be done carefully.
How COIL TEMP SENSOR differs from similar codes
COIL TEMP SENSOR concerns the evaporator coil. AIR TEMP SENSOR is the return air probe for the room.
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
Will the evaporator ice up?
The manual does not say. Check for frost and call for service.
Can ENTER fix the alarm?
It only silences it for 1 hour.
Is it the same as SUCTION TEMP SENSOR?
No. That is the probe on the suction line. This is the one on the coil.
Need help with Kolpak COIL TEMP SENSOR?
A technician confirms the cause on site and gives you the price in writing before any work starts.