Bally Walk-In Cooler Error Code A2A: AU2 Temp Sensors Alarm
A2A, AU2 Temp Sensors Alarm, on a Bally walk-in evaporator with the SmartVap+ controller means auxiliary temperature sensor 2 is shorted or open. The manual lists the trigger only. Check what that second sensor is for and call a technician.
Low: an auxiliary sensor has failed while the main cooling sensors are separate.
- Code
- A2A
- Maker
- Bally
- Equipment
- Walk-in coolers & freezers
- Applies to
- SmartVap+ evaporator controller (on-board display / dashboard display), used with Bally walk-in evaporators
What does Bally error code A2A mean?
A2A covers the second auxiliary temperature input on SmartVap+. The controller checks the AU2 sensor's electrical signal the same way it checks its main sensors, and a reading that looks shorted or open raises the AU2 Temp Sensors Alarm and displays A2A. The manual's Alarm Status Menu gives only that trigger and no steps. It does not name the location or purpose of the sensor on AU2. In many walk-in installations an extra sensor is added to watch a point the main return air sensor cannot see, such as a far corner or a product probe, but the manual does not say what yours does. The alarm therefore means the second input has stopped giving a usable temperature, nothing more. The manual lists matching alarms for the first and third inputs as A1A and A3A, and EA2 for the same input used as an external alarm contact.
Affected models and control systems
The SmartVap+ evaporator controller, with its on-board display or dashboard display, on Bally walk-in evaporators that have an auxiliary temperature sensor on AU2. The manual does not say what the sensor is used for.
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
- A2A shows in the active alarm list
- The AU2 temperature reading is missing or looks wrong
- The alarm light stays on although the room is stable
Possible causes
Listed in Bally's documentation
- AU2 temperature sensor shorted or open
Other likely causes — what usually sits behind error code A2A on this control. A technician confirms which one it is before any part is replaced.
- Sensor lead cut or crushed where it runs along the evaporator or door frame
- Connector pulled out during cleaning or restocking
- Ice or condensation inside the sensor connector
- Input still set for a sensor that was removed
Safe checks before calling for service
- Ask the installer or manager which point the AU2 sensor monitors and whether it has been moved or removed.
- Look at the sensor lead in view for cuts, crushed sections or ice, without opening panels.
- Check the temperature at that spot with a separate thermometer.
- Try Clear Alarms (CLA, press and hold) once, and note whether A2A returns.
How a technician diagnoses error code A2A
- Read active alarms and the AU2 input mode.
- Locate the AU2 sensor and inspect its path and connector.
- Measure its resistance at the controller and compare with the sensor curve at the real temperature.
- Check for a pinched, crushed or open cable and for water in the connector.
- Replace the sensor or set the input correctly, then clear the alarm and confirm the reading returns.
- Sensor leads on a walk-in often run through the evaporator housing beside energized wiring.
- If the sensor was removed on purpose, the controller input settings have to be changed to match, which is a configuration job.
How error code A2A differs from similar codes
A2A is the sensor alarm for AU2. A1A and A3A cover the other two inputs, and EA2 is the external alarm for this same input number.
Technical reference
- Document
- SmartVap+ Intuitive Evaporator Control Technology, Operating Instructions (Bulletin B30-SVP-OM-2.05, Part # 1107523)
- Edition
- B30-SVP-OM-2.05, firmware 2.05+, dated 17/09/21
- Models / control
- SmartVap+ evaporator controller (on-board display / dashboard display), used with Bally walk-in evaporators
- Section
- Alarm Status Menu, page 6 of the PDF
- 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 Bally walk-in cooler & freezer error codes
Why does A2A show if the room is fine?
The alarm is about the AU2 sensor circuit, not the room. The room may be holding temperature well.
Is the AU2 sensor the same one as the return air sensor?
No. The return air sensor has its own alarm, ASA.
Can I remove the sensor to stop the alarm?
We would not. Removing it leaves the input open, and the controller settings should be changed by a technician.
Need help with Bally error code A2A?
A technician confirms the cause on site and gives you the price in writing before any work starts.