Danfoss E1/E2/E3

What does Danfoss E1/E2/E3 mean?

On the Danfoss AK-RC 204B/205C temperature controller for walk-in coolers and freezers, E1, E2 and E3 indicate failure of probe 1, 2 or 3 respectively. The manual defines this as an open circuit, crossed circuit, or a temperature outside the limits of the probe. Probe 1 is the cold-room probe, probe 2 the evaporator probe, and probe 3 is configured by parameter I20.

Symptoms

• Display shows E1, E2 or E3 for the affected probe.
• The corresponding temperature reading is missing or invalid.
• Regulation or defrost tied to the failed probe is disturbed.
• Acoustic alarm and/or alarm relay activate per the controller's message settings.

Common causes

• Probe wiring is open-circuit (broken cable or loose terminal).
• Probe is crossed or short-circuited.
• Measured temperature is outside the probe's valid range.
• Failed temperature probe (cold-room, evaporator, or probe 3).

Diagnostic steps

1. 01

   Identify the failed probe

   Note whether E1 (cold room), E2 (evaporator), or E3 (per I20) is shown to target the right sensor.

2. 02

   Inspect the probe wiring

   Power down and check the affected probe's cable and terminals for open or crossed connections and corrosion.

3. 03

   Measure the probe

   Disconnect the probe and measure its resistance; an open, shorted, or out-of-range value confirms a failed probe.

4. 04

   Replace the probe

   Fit a new probe of the correct type in the same position, route the cable clear of power wiring, and confirm the error clears.

When to call a professional

Probe 1 failure in particular disturbs core temperature control of a walk-in room, risking stored product. If a probe is hard to reach, or the error returns after replacement, a refrigeration technician should confirm the probe type, wiring, and the I20 configuration for probe 3. Trained diagnosis ensures the cold room holds temperature and that defrost based on the evaporator probe continues to work correctly.