Carel AL37

What does Carel AL37 mean?

AL37 is the thermal cutout alarm for Condenser Fan 1 in the Carel Standard Air-Conditioners program. It activates when the digital input wired to the fan motor's thermal overload opens, indicating the motor has overheated or drawn excessive current. The controller stops Condenser Fan 1 immediately. Without condenser fan cooling, the unit's ability to reject heat is reduced, and high-pressure alarms may follow if the compressor continues running.

Symptoms

• AL37 displayed on pCO terminal with Condenser Fan 1 stopped
• Condenser fan motor not running; possible audible silence from condenser section
• Rising discharge pressure on Circuit 1 if compressor remains active

Common causes

• Condenser fan motor thermal overload tripped due to sustained overcurrent from a seized or failing motor bearing
• High ambient temperature combined with a marginally sized motor causing repeated thermal trips
• Supply voltage out of specification causing higher motor current draw
• Wiring fault on the fan motor overload digital input to the pCO board

Diagnostic steps

1. 01

   Allow the motor to cool

   Thermal overloads require a cooldown period before they can be reset. Allow at least 15–20 minutes before attempting to reset the overload device on the fan motor.

2. 02

   Inspect fan motor and blade

   Check that the condenser fan blade spins freely by hand with the power off. A seized bearing or obstructed blade will cause the motor to draw locked-rotor current and overheat immediately on restart.

3. 03

   Check supply voltage and motor current

   Measure supply voltage at the fan motor contactor. Measure running current on the next restart and compare against the motor nameplate full-load amperage. Excessive current confirms motor or electrical fault.

4. 04

   Reset the thermal overload device

   Once the motor has cooled and the mechanical cause is resolved, press the reset button on the thermal overload relay or motor protector. Confirm it re-latches before restoring power.

5. 05

   Reset AL37 on the pCO controller

   After the overload device is reset and the root cause resolved, press ALARM on the pCO terminal to clear AL37. Verify the fan restarts and monitor for repeat trips.

When to call a professional

If the fan motor trips again within the first hour of operation after reset, it has likely failed internally and requires replacement. Motor winding testing and replacement should be performed by a qualified electrical technician. Do not bypass the thermal overload device — this protection prevents motor winding burnout and potential fire.