F42 Fault — Coding resistance fault

What does F42 mean?

A coding resistance fault has occurred, possibly in combination with F.70 (Invalid DSN). This indicates incorrect coding resistors for gas type or an issue with their connection.

• Incorrect DSN setting
• Incorrect coding resistor on board for gas type
• Incorrect coding resistor next to the Expansion vessel

Click steps to track your progress.

1. 1

   Check that the DSN (Device Specific Number) is set correctly (requires installer access).

2. 2

   Verify the coding resistor on the PCB is correct for your gas type (Yellow Nat Gas 806 Ohms / Grey LPG 1180 Ohms).

3. 3

   Try unplugging and then replugging the coding resistor located next to the Expansion vessel.