Bally Walk-In Cooler Error Code CoA: Communication Error
CoA, Communication Error, on a Bally walk-in evaporator with the SmartVap+ controller means bonded controllers have lost communication with each other for one minute or more. The manual says it applies only to bonded controllers. Check the room temperature and call a technician.
Medium: the bonded controllers are no longer coordinating, though each evaporator may still run.
- Code
- CoA
- 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 CoA mean?
On a walk-in with more than one evaporator, SmartVap+ controllers can be bonded, which links them so they act together, for example by defrosting in step. Bonded controllers keep talking to each other over their connection. If that communication drops for one minute or more, a controller raises the Communication Error alarm and shows CoA. The manual's Alarm Status Menu states that this applies only to bonded controllers, so a single evaporator on its own should never show it. No repair steps are given. What the manual does not say is how each controller behaves while the link is down, whether it runs on its own settings or waits for the others. Treat the walk-in as running but not coordinated, and watch the room temperature until a technician checks the link.
Affected models and control systems
The SmartVap+ evaporator controller, with its on-board display or dashboard display, on Bally walk-in evaporators, only where controllers are bonded together. The one-minute trigger comes from the manual's Alarm Status Menu.
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
- CoA shows in the active alarm list on one or more controllers
- Evaporators on the same room defrost or run out of step
- The alarm light is red or yellow
Possible causes
Listed in Bally's documentation
- Only for bonded controllers: no communication between controllers for one minute or more
Other likely causes — what usually sits behind error code CoA on this control. A technician confirms which one it is before any part is replaced.
- Communication cable between the controllers unplugged or damaged
- Connector loose or corroded at one of the controllers
- One controller powered off or restarting
- Cable run near high-voltage wiring picking up interference
Safe checks before calling for service
- Check whether all the evaporator controllers in the room are powered and their displays are lit.
- Scroll active alarms on each controller and note which ones show CoA.
- Watch the room temperature and see whether all evaporators are cooling.
- Do not unplug or move communication cables. Note the affected controllers for the service call.
How a technician diagnoses error code CoA
- Read alarms on all bonded controllers and note which have lost the link.
- Confirm each controller is powered and at the same firmware level.
- Check the communication cable, connectors and terminations between controllers.
- Check for interference from nearby high-voltage wiring and for a damaged cable shield.
- Repair the link, clear alarms and confirm the controllers stay in contact.
- The communication wiring runs inside evaporator housings next to energized wiring, and should not be handled by an operator.
- Bonded controllers share settings, so reconfiguring a link needs someone who knows the site's layout.
How error code CoA differs from similar codes
CoA applies only where controllers are bonded. PrF is a different communication alarm, between the basic display and the controller.
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
Does CoA mean one evaporator has stopped?
Not necessarily. The manual says communication between bonded controllers was lost for a minute or more, not that cooling stopped.
My room has only one evaporator. Why CoA?
The manual says CoA is only for bonded controllers. If one evaporator shows it, the controller may be set to bond.
Is CoA the same as PrF?
No. CoA is between bonded controllers. PrF is between the basic display and the controller.
Need help with Bally error code CoA?
A technician confirms the cause on site and gives you the price in writing before any work starts.