Unox AF03

What does Unox AF03 mean?

AF03 is the chamber temperature probes alarm. The control board has lost a valid reading from a cooking chamber temperature probe — typically because the probe is disconnected, out of range, or failed — so the oven stops to avoid uncontrolled heating. The chamber probes connect to sockets P19 (CMB1) and P16 (CMB2).

Symptoms

• AF03 shown on the control panel
• Oven will not heat or hold temperature
• Erratic or implausible chamber temperature reading
• Alarm persists across restarts

Common causes

• Temperature probe disconnected from socket P19 (CMB1) or P16 (CMB2)
• Damaged or open chamber temperature probe
• Probe resistance out of specification
• Wiring fault between the probe and the board
• Faulty power board

Diagnostic steps

1. 01

   Power down and check probe connections

   Turn off the power supply, open the back of the oven and confirm the temperature probes are connected to socket P19 (CMB1) and P16 (CMB2).

2. 02

   Reconnect and retest

   If a probe is unplugged, reconnect it and test the oven before going further.

3. 03

   Measure probe resistance

   Disconnect each probe and measure it with a multimeter set to ohms; the correct value is about 110 Ω at 25 °C (77 °F). Use the Pt100 resistance table to verify at other temperatures.

4. 04

   Replace a faulty probe

   If a probe is out of specification, replace the damaged temperature probe and retest.

5. 05

   Replace the power board

   If the probes read correctly but the alarm persists, replace the power board.

When to call a professional

AF03 may just be an unseated probe connector, but confirming probe resistance and ruling out the power board requires opening the oven, accessing the boards, and using a multimeter against the Pt100 table. If reseating the connector does not clear it, have a qualified Unox technician measure the probe and board.