Ako E13

What does Ako E13 mean?

E13 indicates that probes S1 and S2 are reading similar temperatures — the temperature difference between the cold-room probe (S1) and the evaporator probe (S2) is too small for the SELFDRIVE system to function correctly. This is functionally equivalent to E11 but is specifically assigned in some controller firmware variants (AKO-16526 series) to the S1–S2 differential failure. SELFDRIVE calibration is suspended and the controller falls back to standard regulation.

Symptoms

• E13 appears on the display.
• SELFDRIVE calibration cannot proceed due to insufficient S1–S2 temperature differential.
• Controller falls back to standard temperature regulation.
• Alarm relay activates.
• S1 and S2 are reading close to the same temperature.

Common causes

• Probe S2 (evaporator probe) incorrectly positioned and reading air temperature close to S1 (most common).
• Evaporator heavily iced, insulating S2 from the coil surface.
• S1 and S2 probes physically swapped at the controller terminals.
• Refrigerant shortage causing the evaporator to warm toward cold-room temperature.
• Blocked airflow over the evaporator reducing the coil-to-air temperature differential.

Diagnostic steps

1. 01

   Verify probe S2 position on the evaporator coil

   Confirm S2 is properly clipped to the evaporator coil. The probe must contact the coil to read the true coil temperature rather than air temperature near it.

2. 02

   Check S1 and S2 are not swapped at the controller

   Trace the cables from both probes to their terminals on the controller. S1 goes to the cold-room air sensor position and S2 to the evaporator coil probe. Swap back if reversed.

3. 03

   Inspect for evaporator ice blocking S2

   Heavy frost insulates S2 from the coil metal. Initiate a manual defrost cycle and recheck the S1–S2 differential after the evaporator is clear.

4. 04

   Check refrigerant system performance

   Observe suction line temperature and pressures. A warm evaporator circuit with near-equal S1 and S2 readings indicates refrigerant shortage or expansion valve failure.

5. 05

   Restart SELFDRIVE calibration after resolving the cause

   After restoring the S1–S2 temperature differential, follow the AKO manual to restart SELFDRIVE calibration and verify E13 clears.

When to call a professional

Call a licensed refrigeration technician if E13 persists after correcting probe positions and performing a defrost cycle, as equal S1–S2 temperatures are a reliable indicator of low refrigerant charge or a failing expansion valve — both requiring refrigerant system diagnosis by a certified technician.