Carel AL02 Error Code

What does Carel AL02 mean?

AL02 is the general compressor alarm for Compressor 2 in the Carel Standard Air-Conditioners program. It activates when the digital input assigned to Compressor 2's thermal overload, high-pressure cutout, or circuit breaker opens. The controller immediately stops Compressor 2 to protect it from damage. Reset requires manual intervention at the controller after the protection device has been reset.

Symptoms

• AL02 displayed on pCO terminal with Compressor 2 stopped immediately
• Compressor 2 contactor de-energized; Circuit 2 cooling capacity lost
• Alarm relay activates; buzzer sounds on external terminal

Common causes

• High discharge pressure tripped the high-pressure cutout on Compressor Circuit 2
• Compressor 2 thermal overload operated due to overcurrent or motor winding temperature
• Compressor 2 circuit breaker tripped on electrical fault or sustained overload
• Loose or open wiring on the alarm digital input for Compressor 2

Ask the AskWhiz AI about Carel AL02

AskWhiz

online

Hi — I'm the Refrigeration demo. Ask me anything in this domain.

What causes Carel AL02?Step-by-step fix for Carel AL02?Is Carel AL02 safe to ignore?

MessageHelp me troubleshoot Carel AL02

Diagnostic steps

1. Identify the protection device that operated

   Locate the compressor protection panel for Circuit 2. Check whether the high-pressure cutout, thermal overload relay, or circuit breaker has tripped. The protection device will be in a visible tripped or open state.

2. Investigate and resolve the root cause

   For high pressure: inspect condenser airflow, fan operation, and refrigerant charge. For thermal overload: check supply voltage, current draw, and motor winding resistance. For circuit breaker: verify no electrical fault before resetting.

3. Reset the protection device

   After resolving the root cause, manually reset the high-pressure cutout, thermal overload, or circuit breaker per its manufacturer instructions. Do not bypass or jumper protection devices.

4. Check and re-seat digital input wiring

   With power off, inspect the alarm digital input wire on the pCO board for Circuit 2. A loose wire at the screw terminal will cause a false AL02 that clears with no apparent cause.

5. Reset the controller alarm and verify restart

   Press the ALARM button on the pCO terminal to reset AL02. The safety timer must expire before Compressor 2 restarts. Monitor system pressures and current draw on the first restart cycle.

When to call a professional

If Compressor 2 trips repeatedly on AL02 within hours of each reset, a licensed HVAC/R technician must diagnose the root cause. Recurring high-pressure trips require refrigerant circuit analysis. Repeated thermal overloads may indicate a failing compressor motor. Any situation where the protection device cannot be identified or safely reset must be handled by a qualified technician with proper recovery equipment.