Kolpak Walk-In Cooler Error Code AUX3 SENSOR: Main AUX3 Shorted or Open
AUX3 SENSOR means the Main AUX3 input is set to a temperature input and is shorted or open. The controller cannot get a temperature from that input. Press ENTER to silence the alarm for one hour and have the sensor and its wiring tested.
Low: one auxiliary reading is lost, and the main room controls are not described as affected.
- Code
- AUX3 SENSOR
- Maker
- Kolpak
- Equipment
- Walk-in coolers & freezers
- Applies to
- ArcticFox OEM Controller with Deluxe Display (Kolpak walk-ins)
What does Kolpak error code AUX3 SENSOR mean?
The third Main auxiliary input on an ArcticFox controller can be assigned to read temperature. In that mode the controller continuously checks the sensor circuit. If the circuit looks shorted or open, the reading cannot be real, and the controller raises the text alarm AUX3 SENSOR in the Alarms menu. The alarm names the circuit, which helps: it is the third Main input, not the Display input and not the first or second. It does not name the cause, because the manual lists none. A technician will treat it as a wiring and sensor question first. Until the input reads properly, whatever function uses AUX3 temperature has no valid data. Pressing ENTER quiets the sound for one hour, and the alarm comes back after that if the circuit has not been repaired. It does not clear itself when you press the key.
Affected models and control systems
ArcticFox OEM Controller with Deluxe Display on Kolpak walk-ins. This alarm covers the Main AUX3 input and is listed in the Alarms menu on page 16.
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
- AUX3 SENSOR text in the Alarms menu
- Audible alarm from the display
- No valid AUX3 temperature on the controller
- Alarm back one hour after silencing
Possible causes
Likely causes — what usually sits behind error code AUX3 SENSOR on this control. A technician confirms which one it is before any part is replaced.
- AUX3 sensor unplugged, or its wire broken near the terminal
- Sensor cable pinched by a door, shelf or conduit clamp
- Corroded probe or connector from moisture in the room
- Input left in temperature mode after the sensor was taken out
Safe checks before calling for service
- Press ENTER to silence the alarm. It stays quiet for 1 hour and returns if the circuit is still bad.
- Check visible sensor cable for pinching or damage without moving or cutting anything.
- Think about whether the alarm began after anything was moved in the room.
- Note the alarm text, the start time and the purpose of the AUX3 sensor for the technician.
How a technician diagnoses error code AUX3 SENSOR
- Verify AUX3 IN MODE is a temperature input.
- Inspect the sensor run end to end for physical damage.
- Measure sensor resistance and compare with the chart, then check continuity and isolation of the cable.
- Replace the failed sensor or repair the run, then confirm a stable reading.
- The input terminals sit in the live controller enclosure.
- Diagnosing a sensor circuit requires a meter and resistance chart.
- Mode changes alter how the controller alarms and belong with the installer's documentation.
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
Is AUX3 SENSOR a sign the walk-in is failing?
No. It says one auxiliary sensor input cannot be read. Main cooling is not described as affected.
Why does it return after ENTER?
ENTER silences it for one hour only. The circuit must be repaired for the alarm to end.
How do I tell AUX3 from the others?
The number matches the Main auxiliary input. A technician can trace which sensor is connected to it.
Need help with Kolpak error code AUX3 SENSOR?
A technician confirms the cause on site and gives you the price in writing before any work starts.