Carel AL19

What does Carel AL19 mean?

AL19 on Carel µChiller and pCO chiller controllers indicates a clockboard fault or absence. The controller relies on the real-time clock (RTC) module for time-scheduled operations such as night setback, timed defrost, and maintenance hour counters. When the RTC is absent or has failed, AL19 activates. The alarm is display-only in most configurations but disables all time-based scheduling functions.

Symptoms

• AL19 displayed on the Carel controller.
• Time-based scheduling functions — night setback, timed defrost — are unavailable.
• The controller clock shows incorrect or frozen time.
• Maintenance hour counters may not advance correctly.

Common causes

• RTC module (clock board) not installed or has become unseated from its socket.
• RTC backup battery dead, causing the clock to reset after every power cycle.
• RTC chip or clock board hardware failure.
• Controller firmware incompatibility with the installed clock module version.

Diagnostic steps

1. 01

   Inspect the RTC module installation

   With power off, open the controller and verify the clock board is correctly seated in its socket. Re-seat if it appears loose or displaced.

2. 02

   Replace the RTC backup battery

   Locate the coin cell battery on the clock board. A flat battery causes the clock to reset on every power cut. Replace with the same specification cell (typically CR2032).

3. 03

   Reset the date and time

   After battery replacement, set the correct date and time in the controller's clock menu and verify the settings are retained after a power cycle.

4. 04

   Check for clock board hardware failure

   If the clock board is seated and the battery is good but AL19 persists, the clock board itself may be faulty. Order a replacement Carel RTC module for the specific controller model.

5. 05

   Reset AL19 at the controller

   After fitting a working clock board, reset AL19 and verify scheduled functions resume correctly.

When to call a professional

Contact a Carel-authorized service engineer if the clock board part number is unknown or if replacing it requires controller disassembly beyond standard access. An engineer with Carel tooling can also reflash controller firmware if a compatibility issue between controller software and clock hardware is suspected.