What do Heatcraft Beacon II (Bohn / Larkin) alarm and error codes mean?

Part of the Heatcraft (Bohn/Larkin) walk-in controller codes hub. Same brand, different controller: Heatcraft intelliGen.

Short answer: Beacon II reports on the evaporator board's LED readout with A-codes (alarms about box conditions and start-up) and E-codes (sensor, superheat, compressor-safety and wiring errors). If the optional wall-mounted Smart Controller is fitted, it repeats alarms as text — *BOXHI, *INFLT, +COMM+ — shows "CALL FOR SERVICE" with the system number, and sounds a buzzer.

Which machines use it?

Beacon II is Heatcraft's previous-generation smart refrigeration system, shipped for years on walk-in evaporators and condensing units branded Bohn and Larkin (plus Climate Control and Chandler). Huge numbers of these are still running in restaurants and stores, so these codes come up constantly on older boxes. The evaporator control board reports through a simple two-digit readout: A-codes (A1–A4) are alarms about box conditions, E-codes (E1–E9) are equipment faults like failed sensors or tripped compressor safeties. On multi-evaporator installs, which board shows the code tells you where the problem is. Practical tip: write down the exact code and whether the compressor is running before resetting anything — several Beacon II faults pump the system down and keep it off until repaired.

The Beacon II Smart Controller is the optional wall-mounted LCD display that ties into Beacon II evaporator boards on Bohn and Larkin walk-in systems, letting staff monitor several coolers and freezers from one panel outside the box. Instead of two-digit codes it shows scrolling text messages — like *BOXHI or *INFLT with "CALL FOR SERVICE" — plus the system number affected, and sounds a buzzer. Remember it is a messenger: the fault it reports lives at the evaporator board or refrigeration system it monitors, not in the display itself. Practical tip: press CLEAR to silence the buzzer, but write down the message and system number first — that pairing tells the technician exactly which unit to walk to.

How do you read and clear the display?

What matters most is whether the system is still allowed to run. With a failed suction sensor, room sensor (on the master board) or pressure transducer, Beacon II pumps down and stays off until the fault is cleared. With an oil-pressure or high/low-pressure cutout it pumps down and retries three times, each after the 4-minute hold-off; after the fourth try the alarm contacts close and the alarm is displayed. Once the repair is done, clear it by cycling the system through SERVICE mode.

How do you enter the parameter menu?

Beacon II is programmed at the evaporator board itself with three controls: the PROGRAM REVIEW button, the SELECT knob and the ENTER button. From the manual's programming section:

1. Press PROGRAM REVIEW. The set-point item's code appears on the LED display, and after a few seconds its current value. Each further press moves to the next item.
2. Turn the SELECT knob to change the value.
3. Press ENTER to store it. If you don't press ENTER, the value is not saved.

The items, in order: A-E defrost type (air or electric); rEF refrigerant; bot box temperature; SUP superheat; SLA board is a slave (yes/no); ddF demand defrost; dFn defrosts per day; dFF defrost fail-safe time (10–200 min); dFt defrost end temperature (40–100 °F); dFS defrost delay start; ALH / ALL alarm high / low; ALt alarm time; F-C units; FnS off-cycle fan stir.

Heatcraft tells installers to put every board in SERVICE mode while programming set points (press FORCE SERVICE twice; CLEAR starts the system cooling again) so the changes don't raise alarms mid-way, and to program every slave evaporator as a slave before starting a multi-evaporator system. The optional Smart Controller LCD module carries its own COOLING, DEFROST, PROG REVIEW, MONITOR, ENTER, CLEAR, SETPOINT and TIME buttons and can program most of the same items remotely — except SLA, which must be set on the board.

Every Heatcraft Beacon II code at a glance

14 codes link to a full section below. The other 6 are listed as the manufacturer's manual gives them. Every row comes from the manual cited at the end of this page.

What does each code mean — and what should you do?

How do you diagnose a Heatcraft Beacon II alarm, step by step?

1. Write down the code, the system number and whether the compressor is running before resetting anything.
2. Check sensors with the monitor button. It displays what the suction (SCt), defrost (dFt) and room sensors are reading — compare each against a thermometer at the same point. Or test in stirred ice water: 32,650 Ω at 32 °F; roughly 1,000 Ω higher or lower means replace the sensor. Don't remove sensors from the evaporators to check them.
3. E6 low superheat — Heatcraft's sequence: check the refrigerant type setting; check the coil for ice (defrost settings, defrost sensor, heater amps); check the board's valve step position; check that the expansion valve closes (pump down — does the low-pressure switch open?); check the compressor is actually running; compare the suction sensor with the real suction-line temperature and the transducer with gauges.
4. E7 compressor shut down — which safety? A low-pressure trip points at the refrigerant type, charge, the LPS setting (freezers: 0 psig cut-out, 10 psig cut-in), a stuck or blocked valve, an iced coil or line sizing. A high-pressure trip points at overcharge, non-condensables, the condenser fan motor or blade, a dirty condenser coil, head-pressure or fan-cycling controls, or a liquid-line restriction.
5. +COMM+ and E9 are wiring. The communication wiring runs MULTI OUT to MULTI IN between boards — never OUT to OUT or IN to IN.
6. LED not lit at all: check the disconnect, fuses and breakers, the transformer's primary and secondary voltage, and 24 V at the control board before replacing the board.
7. After service: at start-up the system may cycle off at 2 minutes with a low-superheat error a few times while the expansion valve finds its setting — Heatcraft's instruction is to let it run.

Which parts are usually involved?

What refrigeration is behind these codes?

Every code here is the controller reporting a reading from the refrigeration system. The background is explained once, for every controller on this site: what superheat is and why controllers alarm on it; what subcooling is; how defrost works and what goes wrong.

If it does come to a service call and you're in Nashville, TN or Birmingham, AL, we maintain independently compiled lists of local companies that service walk-in coolers — real businesses with verified contact information, none of whom paid to be listed.