Carel AL67

What does Carel AL67 mean?

AL67 means Circuit 2 is in Prevent mode, a protection state triggered when the condensing temperature or pressure exceeds a programmable prevention threshold. The controller stops all compressors on Circuit 2 and forces condenser fans to maximum speed to reduce condensing pressure. The alarm resets automatically within 10 seconds once conditions return to normal.

Symptoms

• All compressors on Circuit 2 shut off while condenser fans run at maximum speed.
• Controller display shows AL67 or Prevent status for Circuit 2.
• System capacity drops while Circuit 2 is in prevent mode.
• Automatic recovery occurs once condensing pressure drops below the prevent threshold differential.

Common causes

• High ambient temperature causing condensing pressure to exceed the prevent setpoint.
• Condenser coil fouled with dirt or debris, reducing heat rejection efficiency.
• Condenser fan motor failure reducing airflow across the coil.
• Refrigerant overcharge causing elevated condensing pressure.
• Airflow restriction at the condenser inlet or outlet (blocked discharge, recirculation).

Diagnostic steps

1. 01

   Check condensing pressure or temperature reading

   Read the Circuit 2 condensing pressure from the controller display. Confirm it is above the prevent setpoint and not a sensor false alarm.

2. 02

   Inspect condenser fans on Circuit 2

   Verify all condenser fans for Circuit 2 are running and drawing correct amperage. A failed fan motor will prevent the system from recovering from Prevent mode.

3. 03

   Clean the condenser coil

   Inspect the condenser coil for dirt buildup or debris blockage. Clean with coil cleaner and rinse according to the manufacturer's instructions.

4. 04

   Check for airflow recirculation

   Ensure the unit installation allows free discharge of hot air and there is no recirculation path returning hot discharge air to the condenser inlet.

5. 05

   Review prevent setpoint configuration

   Navigate to Circuit 2 protect parameters and verify the prevent setpoint is configured correctly for the installation design conditions.

When to call a professional

If Circuit 2 remains in Prevent mode despite clean coils and operating fans, or if condensing pressures are consistently elevated during normal ambient conditions, contact a licensed refrigeration technician to check refrigerant charge, condenser fan capacity, and system design. Repeated prevent mode events indicate an underlying system problem that requires professional evaluation.