Carel AL43 Error Code

What does Carel AL43 mean?

AL43 on Carel µChiller and pCO chiller controllers indicates that EEV driver 2's expansion valve motor has a fault. The Carel EVD driver monitors motor current during valve stepping operations; if the motor fails to respond correctly — due to an open winding, a mechanical jam, or a wiring break — the driver raises this alarm. Circuit 2 EEV control is disabled, removing automatic superheat regulation for that circuit.

Symptoms

• AL43 displayed on the Carel controller.
• Circuit 2 EEV valve motor is not responding to step commands.
• Superheat on circuit 2 is uncontrolled.
• Circuit 2 may shut down depending on the alarm response configuration.

Common causes

• Broken coil wire inside the EEV valve motor causing an open winding.
• EEV wiring harness connector between the driver and valve loose or disconnected.
• EEV motor jammed mechanically due to debris or excessive scale in the valve seat.
• EEV driver 2 output stage hardware failure.

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Diagnostic steps

1. Check the EEV valve wiring harness

   Inspect the 4-wire or 6-wire cable from EVD driver 2 to the EEV valve. Look for broken conductors, damaged connectors, or connector pins backed out of the housing.

2. Measure EEV motor winding resistance

   Disconnect the valve from the driver and measure each motor winding resistance using the valve manufacturer's specification. Open windings read infinite resistance; confirm against expected values (typically 40–200 Ω per winding depending on valve model).

3. Power-cycle the EVD driver 2

   Switch off the driver, wait 30 seconds, and restore power. The driver will attempt a valve re-homing sequence on startup. Listen or feel for valve movement.

4. Manually command the valve through a full stroke

   Using the EVD driver's manual mode or the controller service menu, command the valve fully open then fully closed. Resistance or stuttering indicates a mechanical or electrical fault in the valve.

5. Replace the EEV valve if windings are open or motor is jammed

   Install a compatible Carel EEV valve with the correct valve model for the refrigerant and system capacity.

When to call a professional

EEV replacement requires recovery of refrigerant from the affected circuit before removing the valve and brazing in a replacement — all operations requiring an F-Gas certified engineer. An uncorrected AL43 on circuit 2 causes loss of superheat control and risks compressor damage from liquid flood-back.