Danfoss E1: Danfoss EKC 202C Error Code E1

Symptoms

Controller displays E1, indicating the S3 sensor (defrost termination) is open or shorted. The controller cannot execute automatic defrost termination and will fall back to time-based defrost only.

Possible Causes

Defrost termination sensor S3 wiring damaged or disconnected
Sensor S3 has failed and reads open circuit or short circuit
Terminal block corrosion causing intermittent connection
Electrical noise or moisture in the sensor conduit

Troubleshooting Steps

Step 1: Check the S3 sensor wiring at the controller terminals - verify continuity
Repair or replace damaged wiring between sensor and controller
Step 2: Measure S3 sensor resistance at room temperature - NTC type should read approximately 10k ohm at 25C
Replace sensor if resistance is out of specification
Step 3: Inspect terminal block for corrosion, moisture, or loose connections
Clean terminals and apply dielectric grease
Step 4: Verify sensor is properly positioned in the evaporator coil sensor well
Reinsert sensor to proper depth and secure

How to Reset

To reset E1: 1) Press any key on the controller. 2) The alarm will clear if the sensor is now reading correctly. 3) The controller resumes normal operation with S3-based defrost termination.

Common Replacement Parts

084G4000: Danfoss EKC 202C temperature sensor NTC 10k, 3m cable (Verify sensor type matches controller setting)
084G4002: Replacement terminal block for EKC series (Use only Danfoss-approved replacement parts)

Frequently Asked Questions

Q: How do I know if the S3 sensor is faulty?
Measure the resistance across the sensor terminals. At 25C (77F), a good NTC 10k sensor should read approximately 10,000 ohms. An open circuit (infinite resistance) or short circuit (near 0 ohm) indicates a failed sensor.
Q: Can the system run without the S3 sensor?
The system can operate temporarily with time-based defrost only, but this is less efficient and may cause coil icing. Replace the sensor as soon as possible.

Danfoss EKC 202C Error Code E1