Danfoss E18 Error Code

What does Danfoss E18 mean?

E18 indicates the S3 sensor on a Danfoss EKC controller is short-circuited. The input reads near-zero resistance, so the S3 signal is treated as invalid. On superheat controllers this disturbs the superheat calculation, and the alarm relay activates at high priority while the front-panel LEDs flash to mark the regulation error.

Symptoms

• Display shows E18 when the alarm is recalled.
• S3 temperature reading is pinned at an extreme or invalid value.
• Front-panel LEDs flash to indicate the regulation error.
• Superheat regulation is unreliable while S3 is shorted.

Common causes

• S3 cable insulation has failed, shorting the conductors.
• Moisture or water ingress at the S3 sensor or terminal.
• Internally short-circuited S3 temperature sensor.
• Pinched or crushed cable shorting against metal.

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Diagnostic steps

1. Recall the alarm code

   Press the top button to display E18, then press again to cancel the active alarm.

2. Inspect the S3 cable for shorts

   Power down and examine the S3 cable for crushed, pinched, or water-damaged sections.

3. Measure the S3 sensor resistance

   Disconnect S3 and read its resistance; a value near zero confirms a short in the sensor or cable.

4. Replace the S3 sensor

   Fit a new sensor of the correct type, protect the cable from moisture, and confirm E18 clears once power is restored.

When to call a professional

A shorted S3 sensor undermines the superheat control that protects the compressor, so it should not be left active. If the short cannot be isolated or the sensor sits in a sealed location, have a refrigeration technician trace and replace the circuit. They will confirm the controller reads S3 correctly and re-verify regulation. Untrained work inside the live panel risks shock and incorrect re-commissioning.