Carel E7

What does Carel E7 mean?

On Carel refrigeration controllers (source document 0300100EN.pdf), the E7 alarm indicates that probe DeS2H (the defrost S2 probe) is faulty or disconnected. This probe measures the evaporator temperature used to terminate defrost cycles by temperature. When E7 is active, defrost termination by temperature is unavailable and the controller may fall back to a time-limited defrost or disable defrost depending on configuration.

Symptoms

• E7 displayed on the controller alternating with temperature.
• Defrost termination by temperature is unavailable; cycle runs to time limit.
• Alarm relay activates.
• Evaporator temperature monitoring for defrost control is lost.

Common causes

• DeS2H probe wiring open-circuit or disconnected at the probe or controller terminal.
• NTC sensor element failed — open or short circuit.
• Probe cable damaged by ice formation or mechanical contact during defrost cycle.
• Corrosion on the probe connector terminal from repeated freeze-defrost cycling.

Diagnostic steps

1. 01

   Locate and inspect the DeS2H probe

   Find the defrost S2 probe clipped to the evaporator coil. Check for ice encasement, physical damage, or loose mounting.

2. 02

   Measure probe resistance

   Disconnect the probe from the controller and measure resistance across the two leads. A healthy NTC at 0 °C reads approximately 6 kΩ; open or short confirms failure.

3. 03

   Inspect the cable to the controller

   Trace the cable from the evaporator to the controller terminal. Look for cuts, pinch damage from ice, or corroded terminals.

4. 04

   Replace the defrost probe

   Install a compatible Carel NTC probe in the same evaporator location. Secure it with a probe clip so it has firm thermal contact with the coil.

5. 05

   Reset and confirm defrost operation

   Clear the E7 alarm, trigger a manual defrost cycle, and verify the controller terminates defrost based on the probe reaching the configured end-defrost temperature.

When to call a professional

Escalate to a refrigeration technician if E7 persists after probe replacement, or if repeated probe failures occur — indicating the evaporator environment is damaging probes faster than normal due to ice bridging or aggressive defrost temperatures. A technician should also verify defrost cycle configuration to ensure it does not risk compressor liquid slugging when probe-based termination is unavailable.