What does E1 mean on an AKO refrigeration controller?

E1 on AKO controllers (AKO-D-14, AKO-D-145, AKO-16524A) signals a Probe 1 fault — the primary control sensor has gone open-circuit, short-circuit, or out of range (NTC: above +110 °C or below -55 °C; PTC: above +150 °C or below -58 °C). Compressor behaviour falls back to parameter C6 (stop, keep running, 24-hour average, or C7/C8 schedule). Disconnect Probe 1 and ohm it against the AKO NTC R-vs-T table, inspect the cable run for damage or moisture ingress, and replace with an AKO-approved probe routed away from power wiring.

What does E2 mean on an AKO controller?

E2 indicates a fault on Probe 2 (the evaporator probe) — open circuit, short circuit, or temperature outside the sensor range. While E2 is active the fans run continuously (F0 and F1 evaporator-temperature shutdown is bypassed) and defrost ends by time only because end-by-temperature is disabled. Inspect the probe cable for cuts and moisture, re-seat the terminal, ohm the probe against the AKO R-vs-T table, and replace if open or out of range. On dual-evaporator AKO-16526 controllers, the equivalent fault on the second evaporator probe S3 is reported as a separate code.

What does E5 mean on an AKO cold-room controller?

E5 is a severe external alarm activated by a digital input configured with parameter P10 or P11 set to 3. Common sources are high-pressure switches, oil-pressure switches, motor protection relays, or remote alarm contacts. The alarm relay and buzzer fire immediately, regulation may halt, and the alarm latches until manually reset — even after the input clears. Identify the connected device from the panel wiring diagram, fix the underlying fault (do not just reset), test continuity of the digital-input wiring for shorts or noise, and confirm P10/P11 are intentionally set to 3.

What does E10 mean on an AKO-16524A or AKO-16526 controller?

E10 is a defrost time-out (Adt) on the first evaporator — the coil did not reach the d4 defrost-end temperature within the d2 maximum defrost time, so ice may remain on the fins. Most common cause is a failed electric defrost heater element. Isolate power, ohm each heater for continuity, confirm the defrost end-probe S2 is clipped to the coil (not hanging in air), and check that d2 is long enough for the installed heater capacity and ice load. On the AKO-16526 second-evaporator variant, the equivalent fault is E20.

What does E12 mean on an AKO advanced controller?

E12 means the SELFDRIVE self-calibration system could not complete on the first evaporator because of system instability — typically door openings during the calibration window, expansion valve hunting causing suction-pressure oscillations, heavy product loading, refrigerant charge imbalance, or Probe S2 positioned in a fan blast zone. The controller falls back to standard regulation. Run calibration overnight, check the expansion valve for hunting, reposition S2 to a thermally stable point on the coil, and verify refrigerant charge before retrying SELFDRIVE.

What does E16 mean on an AKO-16524A or AKO-16526 controller?

E16 is raised when the number-of-evaporators parameter has been changed (1→ 2 or 2→ 1), invalidating the previous SELFDRIVE calibration data and any probe / relay assignments tied to the former count. After a deliberate change, verify the parameter matches the physical installation, re-check S1 / S2 / S3 probe assignments, confirm compressor / defrost / fan relay outputs are correctly mapped, save, and run a fresh SELFDRIVE calibration. If E16 appears without a deliberate change, suspect parameter corruption — power-cycle and re-verify the full configuration.

What does E21 mean on an AKO-16526 dual-evaporator controller?

E21 is the second-evaporator equivalent of E11: probes S1 (cold-room air) and S3 (second evaporator coil) are reading similar temperatures, leaving insufficient differential for SELFDRIVE to calibrate the second evaporator. Confirm S3 is firmly clipped to the coldest accessible point on the second coil and not hanging in free air, trace S1 and S3 cables to verify they have not been swapped at the controller, run a manual defrost on the second evaporator if it is heavily iced, and check the second-circuit suction line for refrigerant shortage symptoms before retrying calibration.

How do I reset the AKO controller password / access the parameter menu?

AKO controllers use a multi-level parameter menu protected by an access code. On the AKO-D-14, AKO-D-145 and AKO-16524A, press and hold SET (or the dedicated parameter key) for 5–7 seconds until the access-code prompt appears, enter the user code (default is often “0” for Level 1 user parameters and “-19” or a site-specific value for Level 2 installer parameters), then use the arrow keys to scroll and SET to confirm each value. If the code has been changed and lost, perform a factory reset per the controller manual — this clears all custom parameters, so back up your configuration via AKONet or the front panel before resetting. Re-enter every parameter from your commissioning record afterwards.

How do I configure an AKO controller after replacing it (AKO configured probe types and parameters)?

After fitting a replacement AKO controller, configure the basic parameters in this order: (1) probe type — confirm whether the installed probes are NTC or PTC and set the corresponding parameter (the wrong probe-type setting causes immediate E1/E2/E3 alarms because readings fall outside valid limits); (2) setpoint SP and differential dIF; (3) high (A1) and low (A2) temperature alarm thresholds plus alarm delay (A5); (4) defrost type, interval (d0 or d1), maximum duration (d2), drip-off time (d3) and defrost end temperature (d4); (5) fan parameters F0–F5 for compressor-linked behaviour, defrost behaviour and door-contact response; (6) digital input function parameters P10/P11 (or PA/Pb) for door contacts, remote stop, or external alarms. Always verify against the original commissioning record.

What does AL1 mean on an AKO multi-alarm controller (AL1–AL6 series)?

AL1 is the maximum temperature alarm on AKO controllers in the AL1–AL6 multi-alarm series — it triggers when the control probe reads above the parameter A1 threshold for longer than the A5 alarm delay. AL1 is compliant with RSIF and EN refrigeration regulations and is the primary food-safety alarm. Verify the temperature is genuine with an independent thermometer (rule out an E1 probe fault first), inspect the refrigeration system (compressor running, condenser fans operating, condenser coil clean, evaporator not blocked with ice), check door seal condition and opening frequency, and confirm A1 is set appropriately for the stored product. The complementary AL3 minimum-temperature alarm covers the freeze-damage case.

Quick Answer

AKO refrigeration controllers (AKO-D-14, AKO-D-145, AKO-16524A and AKO-16526 series) display fault codes E1–E25 for probe and SELFDRIVE faults, AL1–AL6 for high and low temperature alarms, HI / LO for threshold alarms, EE for EEPROM corruption, and F0–F10 as fan-control parameters. E1, E2, E5, E10 and E16 are the highest-volume technician queries.

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By Nichita Herput

Co-founder & CEO · Reviewed May 2026

What error codes does AKO display?

Probe 1 fault — ohm against AKO NTC/PTC R-vs-T table and replace with AKO-approved probe

Probe 2 (evaporator) fault — fans run continuously, defrost end-by-temperature disabled

Severe external alarm — fix the connected safety device (HP / LP / oil) before manual reset

E10

Defrost time-out (Adt) on first evaporator — ohm defrost heaters and verify S2 position

E12

SELFDRIVE calibration failed — check expansion valve hunting and avoid door openings

E16

Evaporator-count parameter changed — re-verify probe / relay assignments and run SELFDRIVE

E21

Similar S1 and S3 readings on dual-evaporator — check S3 position and second-circuit charge

AL1

Maximum temperature alarm — inspect refrigeration system, door seals, and A1/A5 settings

High-temperature alarm above A1 — verify with independent thermometer before diagnosing system

EEPROM error — power-cycle 30 s, re-enter parameters from commissioning record, replace if persistent

Common questions about AKO equipment

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