Home › Commercial Refrigeration Guide › Refrigeration Error Codes › Heatcraft Beacon II Error and Alarm Codes
Updated October 14, 2026
Quick answer
Heatcraft Beacon II walk-in refrigeration boards show A-codes for alarms and E-codes for errors. A1 is high box temperature, A2 low box temperature, A3 a system start-up failure and A4 an input fault. E1 to E5 are sensor faults, E6 is low superheat, E7 is a compressor shutdown on a pressure switch, and E9 is a multi-evaporator wiring error. Box temperature alarms clear on their own once the temperature recovers.
Which systems this page covers
Beacon II is Heatcraft's electronic control for walk-in cooler and freezer refrigeration systems, sold under Heatcraft brands such as Bohn, Larkin, Chandler and Climate Control. The board sits in the evaporator (unit cooler) inside the walk-in and shows two-character codes on an LED display. This page uses Heatcraft's Beacon II Refrigeration Systems Installation and Operation Manual, H-IM-79G (June 2020, Part No. 25001401).
Heatcraft's newer IntelliGen controller and the Beacon II Smart Controller (a separate LCD panel with codes like *BOXHI) use different displays. They are not covered here.
Beacon II alarm codes (A-codes)
An alarm closes a set of dry contacts on the board, which can drive a light, buzzer or monitoring system.
| Code | Meaning (per Heatcraft) | How it clears |
|---|---|---|
| A1 | High box temperature: room temperature stayed above the high alarm setting (ALH) for the alarm time (ALt) | Automatically, once box temperature falls back below the alarm setpoint |
| A2 | Low box temperature: room temperature stayed below the low alarm setting (ALL) for the alarm time | Automatically, once box temperature rises above the alarm setpoint |
| A3 | System start-up failure: the compressor pumps down and retries after 4 minutes; after 4 failed restarts A3 shows, and the system keeps trying | Service Mode or turning off power |
| A4 | Input fault: box temperature sensor, suction temperature sensor or pressure transducer open or not installed | Replacing the failed sensor or transducer |
| (power failure) | Loss of power to the evaporator also closes the alarm contacts | Restoring power |
Beacon II error codes (E-codes)
| Code | Meaning (per Heatcraft) |
|---|---|
| E1 | Room temperature sensor shorted, open or not installed |
| E2 | Defrost temperature sensor shorted, open or not installed |
| E3 | Suction temperature sensor shorted, open or not installed |
| E4 | Suction pressure transducer shorted, open or not installed |
| E5 | Outdoor temperature sensor shorted |
| E6 | Low superheat during cooling |
| E7 | Compressor shut down: high or low pressure switch open, or oil pressure switch open |
| E9 | Multi-in / multi-out wiring error (systems with more than one evaporator) |
At power-up the board checks its sensors. If the suction sensor or room sensor is shorted, open or missing, the system pumps down, shuts off, and will not restart until the fault is cleared or the breaker is reset.
A1: the walk-in is warm
A1 is the alarm owners see most, and it is a symptom, not a cause. Before calling, check the things that warm a box without any equipment failure: a door left open or not sealing, a torn gasket, a heavy load of warm product, or a recent defrost. Then check the evaporator inside the box: is the coil a solid block of ice, and are the fans turning? If the coil is iced over or the fans are stopped, call for service.
While you wait, protect the food. Move product that must stay at 41°F or below to another cooler, and log temperatures. Our guide to food safety when refrigeration fails covers the time rules.
E6: low superheat
Low superheat means liquid refrigerant may be reaching the compressor, which can damage it. Heatcraft's troubleshooting guide checks, in order: the refrigerant type programmed on the board, ice on the coil (defrost the coil and check defrost settings, the defrost sensor and heater amps), the electronic expansion valve position, whether the valve closes on pumpdown, whether the compressor runs, and the accuracy of the suction sensor and pressure transducer. Only the ice check is something an owner can see; everything else is technician work with gauges.
E7: compressor shut down on a safety switch
E7 means a pressure safety opened. High pressure on an outdoor condensing unit often comes from a dirty condenser coil or a failed condenser fan, especially on hot days. Low pressure can come from low refrigerant charge or an iced-over evaporator. Look at the condensing unit: is the coil matted with dust or debris, and is the fan turning? Do not reset pressure switches repeatedly. A switch that keeps tripping is protecting the compressor.
Service Mode and SEr
Each condensing unit has a SERVICE switch. Closing it pumps the system down and shuts it off, and the board displays SEr. The evaporator fans and heaters also turn off. The system will not restart until the switch is returned to NORMAL. If you see SEr and no one is working on the system, someone may have left the switch closed.
When to call a technician
Call a technician for A3, A4, any E-code, or A1 that does not clear within an hour once the door is closed and the box is not overloaded. E6 and E7 protect the compressor, so get them looked at the same day.
Open 7 days, 8 AM to 5 PM, with emergency service until 9 PM. CA Lic. #776244.
Frequently asked questions
What does A1 mean on a Heatcraft walk-in?
A1 is a high box temperature alarm: the walk-in stayed above its high alarm setting for the programmed alarm time. It clears by itself once the temperature comes back down.
What is E6 on a Beacon II?
E6 is low superheat during cooling. It can mean an iced coil, a wrong refrigerant setting, or an expansion valve or sensor problem, and it needs a technician.
Why does my walk-in controller say SEr?
SEr means the system is in Service Mode, usually because the SERVICE switch at the condensing unit is closed. The system stays off until the switch returns to NORMAL.
How do I clear an A3 alarm?
Heatcraft says placing the system in Service Mode or turning off power clears A3. Because A3 means the system failed to start four times, the cause still needs to be found.
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