Bally Walk-In Cooler Error Code A1A: AU1 Temp Sensors Alarm
A1A, AU1 Temp Sensors Alarm, on a Bally walk-in evaporator with the SmartVap+ controller means auxiliary temperature sensor 1 is shorted or open. The manual lists the trigger only. Find out what that sensor measures on your walk-in and call a technician.
Low: an auxiliary sensor has failed, and the controller's main cooling sensors are separate.
- Code
- A1A
- 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 A1A mean?
Besides the sensors it needs for refrigerant control, SmartVap+ has auxiliary inputs that can carry extra temperature sensors. The AU1 sensor is the first of these. The controller checks its signal, and if the circuit looks shorted or open it raises the AU1 Temp Sensors Alarm and shows A1A. The manual's Alarm Status Menu lists the alarm and its trigger only. It does not say what the AU1 sensor measures; that depends on how the walk-in was set up, and it might watch a second room point, a discharge air temperature or a condensing unit. Because of this, the alarm tells you a sensor circuit is broken but not what information the controller has lost. The sensors on AU2 and AU3 report as A2A and A3A, and EA1 is a different alarm for the same input when it is 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 AU1. 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
- A1A shows in the active alarm list
- A temperature reading on the controller for the AU1 point is missing or odd
- The alarm light is on while the room holds temperature
Possible causes
Listed in Bally's documentation
- AU1 temperature sensor shorted or open
Other likely causes — what usually sits behind error code A1A on this control. A technician confirms which one it is before any part is replaced.
- Sensor lead damaged, pinched or pulled loose at its connector
- Sensor lead cut when the evaporator housing was closed
- Moisture or ice in the sensor connector
- The AU1 input is set to read a sensor, but no sensor is installed
Safe checks before calling for service
- Ask who installed the walk-in what the AU1 sensor is for and where it is placed.
- Look at the sensor and its lead if you can see them without opening panels, for damage or ice.
- Check the real temperature at that point with a separate thermometer.
- Try Clear Alarms (CLA, press and hold) once. If A1A returns, note it for the service call.
How a technician diagnoses error code A1A
- Read active alarms and the AU1 input mode, confirming it is set as a temperature sensor.
- Find the AU1 sensor and inspect it and its wiring.
- Measure the sensor's resistance at the controller against its curve at the actual temperature.
- Check the connector and cable run for pinching, moisture or an open conductor.
- Replace the sensor or correct the setting only after the test, then clear the alarm.
- Measuring the sensor involves energized controller wiring in the evaporator housing.
- Whether the input should be reading a sensor at all depends on the controller's configuration and the site's design.
How error code A1A differs from similar codes
A1A is the AU1 temperature sensor alarm. EA1 is the external alarm for the same input number, and A2A and A3A are the sensor alarms for inputs 2 and 3.
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
What does the AU1 sensor measure?
The manual does not say. It depends on how the walk-in was installed, so the installer or technician can tell you.
Is A1A the same as EA1?
No. A1A is about a sensor circuit being shorted or open. EA1 is about the input set as an external alarm being active.
Will the walk-in stop cooling?
The manual does not say that A1A stops cooling. Check the room temperature and the alarm light.
Need help with Bally error code A1A?
A technician confirms the cause on site and gives you the price in writing before any work starts.