Ako E2

What does Ako E2 mean?

The controller has detected a fault on Probe 2 (the evaporator probe). The fault is an open circuit, a crossed/short circuit, or a temperature reading outside the valid range for the sensor type. When E2 is active, fans run continuously, ignoring the F0 and F1 shutdown parameters, while F2 through F4 remain in effect. Compressor behavior depends on parameter C6 configuration.

Symptoms

• E2 alternates with the temperature reading on the display.
• Alarm relay and audible alarm activate.
• Fans run continuously regardless of evaporator temperature.
• Defrost end-by-temperature function is disabled; defrost ends by time only.
• Fan shutdown based on evaporator temperature (F0/F1) stops operating.

Common causes

• Open circuit in the evaporator probe or its cable (most common).
• Short or crossed wiring at the probe connector or terminal block.
• Moisture ingress on the evaporator probe causing resistance shift.
• Probe temperature reading exceeds valid limits (NTC: above +110 °C or below -55 °C; PTC: above +150 °C or below -58 °C).
• Incorrect probe type installed or parameter mismatch with installed sensor.

Diagnostic steps

1. 01

   Isolate and inspect the probe cable

   Disconnect power to the controller. Inspect the entire length of the evaporator probe cable for visible damage, kinks, pinch points, or signs of moisture. Repair or replace damaged cable.

2. 02

   Check terminal connections

   Verify the probe is firmly seated at both the probe connector and the controller terminal block. Clean any corroded contacts and re-terminate if necessary.

3. 03

   Measure probe resistance

   With the probe disconnected, use a multimeter to measure resistance at the probe tip. Compare the reading against the AKO NTC/PTC resistance–temperature table. An open-loop or out-of-range reading confirms probe failure.

4. 04

   Verify probe type matches controller parameters

   Confirm the probe type (NTC or PTC) matches the controller's configuration. A type mismatch produces readings outside valid limits and triggers E2.

5. 05

   Replace the faulty probe

   Install a new AKO-approved replacement evaporator probe. Use only probes supplied by AKO and route the cable separately from power or control wiring. Restore power and verify E2 clears.

When to call a professional

Call a licensed refrigeration technician if the probe and wiring check out mechanically but the fault persists, if moisture has reached the controller terminals or circuit board, or if the evaporator has iced up during the fault period and requires a controlled defrost cycle to restore normal operation. Electrical diagnosis inside the controller enclosure or compressor management changes also require a qualified technician.