Carel AL25

What does Carel AL25 mean?

AL25 is a Condenser 1 Temperature Probe fault alarm on the Carel Standard Air-conditioner (030221426). The temperature sensor monitoring the condensing temperature on refrigerant circuit 1 has produced an invalid signal, triggering this alarm after a 60-second delay. Condenser temperature monitoring is used for high condensing temperature protection and fan speed control.

Symptoms

• AL25 appears on the controller display after the 60-second detection delay.
• Condenser 1 temperature reading shows an invalid value.
• Condenser fan speed control or high-condenser-temperature protection may use fallback behavior.
• Alarm relay activates per relay configuration.

Common causes

• Condenser temperature probe wire disconnected at the controller input terminal.
• NTC sensor element in the condenser coil probe has failed.
• Probe installation in the condenser coil subjected to mechanical damage from vibration.
• Incorrect probe type configured in the controller parameters.
• Probe connection corroded in an outdoor condenser environment.

Diagnostic steps

1. 01

   Inspect probe wiring at the controller

   Check the probe terminal connections for looseness, corrosion, or physical breaks. Outdoor condenser probes are prone to corrosion-related failures at the terminal.

2. 02

   Measure probe resistance at the probe body

   Disconnect the probe from the controller and measure its resistance. For a standard NTC probe, resistance at 25°C is typically 10,000 ohms. An open or very low resistance confirms sensor failure.

3. 03

   Inspect the probe in the condenser coil

   Locate the probe clip or well in the condenser coil. Check for physical damage to the probe body from fin contact or vibration. Reseat the probe if it has shifted out of proper thermal contact.

4. 04

   Verify probe configuration in the controller

   In the service menu, confirm the condenser probe type and alarm limits are correctly configured for the installed probe. Misconfiguration causes valid readings to appear as alarm conditions.

5. 05

   Replace probe and verify reading

   Install a compatible condenser temperature probe. Confirm the condensing temperature reading is plausible relative to ambient conditions before clearing the alarm.

When to call a professional

Contact a refrigeration technician if condenser probe replacement does not clear AL25, or if the alarm is accompanied by actual high condensing pressure conditions. High condenser temperature paired with a valid probe is a refrigerant system fault requiring a complete performance analysis.