Polar King Walk-In Alarm COMMUNICATION ERROR: No Controller Link
COMMUNICATION ERROR is an alarm for bonded KE2 controllers only: there has been no communication between the controllers for one minute or more. The document gives no repair steps. Check that both units have power and that the link cable between them is seated.
Medium: the controllers are not coordinating, and the document does not describe the effect on cooling.
- Code
- COMMUNICATION ERROR
- 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 COMMUNICATION ERROR mean?
Some Polar King walk-ins have more than one KE2 Evaporator Efficiency controller, bonded together so that they share information. In that arrangement each board expects to hear from the other. When there is no communication between the controllers for one minute or more, the Alarms Status Menu lists COMMUNICATION ERROR. The document says this alarm applies to bonded controllers only, so a single-controller box should not show it. The Combo Display names the alarm; the Basic Display shows a red or yellow light. The installation instructions give no cause or steps, and mention the CLEAR ALARMS menu item for clearing. What the controllers do while they cannot talk is not described, so the box temperature is the thing to watch.
Affected models and control systems
Polar King walk-in coolers and freezers with bonded KE2 Evaporator Efficiency Evap OEM controllers, 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 light on the Basic Display
- COMMUNICATION ERROR on the Combo Display
- One evaporator behaving differently from the other
Possible causes
Likely causes — what usually sits behind COMMUNICATION ERROR on this control. A technician confirms which one it is before any part is replaced.
- A link cable between the two boards pulled out or cut
- One controller without power because its breaker or fuse opened
- A connector at either board corroded by washdown moisture
Safe checks before calling for service
- Check whether both controllers show a lit display.
- Look at the breaker or switch that feeds each evaporator.
- Check the box temperature with a thermometer.
- Clear the alarm with CLEAR ALARMS. If COMMUNICATION ERROR returns, note which unit looks dead and arrange service.
How a technician diagnoses COMMUNICATION ERROR
- Read the alarm and confirm both controllers are bonded.
- Check supply voltage at each controller.
- Inspect the communication cable and connectors at both boards.
- Check the bonding configuration of each board.
- Replace the cable or board that fails, then confirm they communicate.
- Each controller is supplied from line voltage control wiring, and testing means opening the evaporator housing. Bonding is a configuration step that needs the installation instructions and the right settings. A dead controller can leave one evaporator unprotected.
How COMMUNICATION ERROR differs from similar codes
COMMUNICATION ERROR applies only to bonded controllers. Every other alarm in this list can occur on a single controller.
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
My walk-in has one controller. Why do I see this?
The document says this alarm is for bonded controllers only. A technician should check the configuration.
Does the box keep cooling?
The document does not say. Check the temperature.
How long before the alarm appears?
After no communication for one minute or more.
Need help with Polar King COMMUNICATION ERROR?
A technician confirms the cause on site and gives you the price in writing before any work starts.