Unox AL04 Error Code

What does Unox AL04 mean?

AL04 is a chamber/resistor temperature probe alarm on the prover accessory. A temperature probe measuring the prover chamber or heating resistor has failed or is disconnected, so the prover stops to avoid uncontrolled heating. The main oven can still be used.

Symptoms

• AL04 shown referencing the prover
• Prover will not heat or hold temperature
• Implausible prover temperature reading
• Alarm persists across restarts

Common causes

• Chamber/resistor probe disconnected
• Probe out of range or failed
• Wiring fault to the probe
• Connector problem

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Diagnostic steps

1. Power down and check the probe

   Turn off power and confirm the prover chamber/resistor probe is connected.

2. Measure the probe

   Measure the probe with a multimeter to confirm it is within range.

3. Inspect the wiring

   Check the wiring between the probe and the prover board.

4. Replace the probe

   Replace the temperature probe if it is out of specification and retest.

When to call a professional

AL04 affects the prover accessory. Confirming the probe and wiring requires accessing the prover electronics; have a qualified Unox technician verify and replace the probe if reconnecting it does not clear the alarm.