Polar King Walk-In Cooler Alarm T2 AIR SENSOR: Shorted or Open
T2 AIR SENSOR is an alarm on the KE2 evaporator control: the return air temperature sensor is shorted or open. The air temperature is what the box temperature alarms depend on. The document gives no steps beyond clearing the alarm, so check the box with a thermometer.
Medium: the box temperature reading is lost, so product temperature should be checked directly.
- Code
- T2 AIR SENSOR
- Maker
- Polar King
- Equipment
- Walk-in coolers & freezers
- Applies to
- Polar King walk-in coolers/freezers with KE2 Evaporator Efficiency Evap OEM board (Basic Display / Combo Display)
What does Polar King T2 AIR SENSOR mean?
The KE2 Evaporator Efficiency board measures the temperature of the air returning to the evaporator with a sensor it names T2. That reading represents the temperature of the walk-in itself, and the high and low air temperature alarms are measured from it. When the sensor wiring is shorted or the circuit is open, the board cannot read it, and the Alarms Status Menu lists T2 AIR SENSOR. The Combo Display shows the words, and the Basic Display shows a red or yellow light. The installation instructions state the trigger, a shorted or open sensor, and no cause or repair. They say alarms can be cleared with the CLEAR ALARMS menu item. Without a valid air reading, the cooler may be running on incomplete information, so a thermometer in the box is the best way to know the real temperature.
Affected models and control systems
Polar King walk-in coolers and freezers fitted with the KE2 Evaporator Efficiency Evap OEM board, with either the Basic Display or the Combo Display. The alarm is listed in the Alarms Status Menu, which is view only, on page 14 of the KE2 installation instructions.
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
- Red or yellow alarm light
- T2 AIR SENSOR listed on the Combo Display
- Box temperature different from what the control shows
Possible causes
Likely causes — what usually sits behind T2 AIR SENSOR on this control. A technician confirms which one it is before any part is replaced.
- A return air sensor splashed during washdown so water reached the connector
- A cable chafed against the fan shroud
- A sensor bulb knocked out of position by stock or cleaning
Safe checks before calling for service
- Check the box temperature with a thermometer placed away from the evaporator.
- Look at the alarm light color or read T2 AIR SENSOR on the Combo Display.
- Clear the alarm with CLEAR ALARMS and see whether it returns.
- If it does, record the thermometer reading and arrange service.
How a technician diagnoses T2 AIR SENSOR
- Read the alarm and the displayed room temperature.
- Compare the displayed air temperature with a reference thermometer.
- Inspect the sensor and cable for damage or moisture.
- Measure sensor resistance and compare it with the chart.
- Replace the sensor if the reading is out of range, then check the alarm history.
- The return air sensor is wired into the evaporator board, and testing it involves disconnecting live control wiring. Comparing readings needs a reference instrument left in the box for a while. If the sensor is fine, the board input may need replacement, which is a controls job.
How T2 AIR SENSOR differs from similar codes
T2 is the return air sensor, which also feeds the HIGH AIR TEMP and LOW AIR TEMP alarms. T1 is the suction sensor and T3 the coil sensor.
Technical reference
- Document
- KE2 Evaporator Efficiency Installation Instructions N.1.1 (posted on polarking.com Downloads as ke2-installation.pdf; authored by KE2 Therm Solutions)
- Edition
- N.1.1 July 2015
- Models / control
- Polar King walk-in coolers/freezers with KE2 Evaporator Efficiency Evap OEM board (Basic Display / Combo Display)
- Section
- Alarms Status Menu (view only), p. 14 (Alarm Status Menu listed p. 13)
- 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 Polar King walk-in cooler & freezer error codes
Is the box temperature safe if T2 alarms?
You cannot rely on the display. Use a thermometer to check.
Does T2 relate to the HIGH AIR TEMP alarm?
The air temperature alarms depend on the room temperature reading, so a lost T2 can affect them.
Can I clear T2 AIR SENSOR myself?
Yes, the document says the CLEAR ALARMS item clears it, but a bad sensor will bring it back.
Need help with Polar King T2 AIR SENSOR?
A technician confirms the cause on site and gives you the price in writing before any work starts.