Carel E1

What does Carel E1 mean?

The E1 alarm indicates that probe S2 (the defrost/evaporator probe) has failed or lost contact with the Carel ir33 controller. The controller cannot read a valid temperature signal from this sensor, so it disables automatic defrost based on probe feedback and falls back to a time-based defrost cycle or halts defrost entirely depending on parameter d0 configuration.

Symptoms

• E1 flashes alternately with the set-point temperature on the controller display.
• Automatic defrost cycles stop triggering normally.
• Buzzer may activate depending on alarm output configuration.
• Defrost termination by probe temperature is no longer available.

Common causes

• Broken or disconnected wiring between probe S2 and the controller terminal.
• NTC sensor element failed open-circuit or short-circuit.
• Moisture or corrosion on the probe connector causing high resistance.
• Probe routed too close to power cables, causing electromagnetic interference.

Diagnostic steps

1. 01

   Inspect the S2 probe wiring

   Trace the probe cable from the evaporator to the controller S2 terminals. Look for chafed insulation, loose terminal screws, or broken conductors.

2. 02

   Measure probe resistance

   Disconnect S2 from the controller and measure resistance across the probe leads with a multimeter. A healthy NTC at 0 °C reads approximately 6 kΩ; open-circuit (OL) or near-zero resistance confirms a failed sensor.

3. 03

   Check controller terminal tightness

   Re-seat and tighten the S2 wiring at the ir33 terminal block. A loose screw is a common cause of intermittent probe faults.

4. 04

   Replace the probe if defective

   Install a compatible Carel NTC replacement probe, ensuring the cable is routed away from power and inductive load cables by at least 3 cm.

5. 05

   Reset the alarm and verify

   Power-cycle the controller or press the alarm reset key. Confirm E1 clears and probe S2 reads a plausible temperature within 30 seconds of restart.

When to call a professional

Call a licensed refrigeration technician if probe replacement does not clear the alarm, if the fault recurs within days of repair, or if the controller board itself is suspected of damage. Repeated E1 alarms with an intact probe can indicate a faulty analog input on the controller board, which requires a qualified technician to diagnose and replace the unit safely without disturbing the refrigerant circuit.