Gas Safe: Gas work, flue work, and PCB replacement on a gas boiler must be carried out by a Gas Safe registered engineer. Homeowners can check obvious items such as heating pressure, condensate overflow, and whether a control is unplugged — then call an engineer.
Always confirm the part number against the boiler GC number and the installation manual before ordering.
Overview
F.92 means the gas-family coding resistor on the PCB does not match the gas family entered in the software. Common after a PCB change or an incomplete gas-family check.
Vaillant meaning: Coding resistor fault (gas family mismatch)
Possible causes
- Wrong or missing coding resistor on the PCB
- Natural gas / LPG family entered incorrectly
- Gas-family check not completed
Possible solutions
- Check which gas the appliance is actually on (meter / tank) against the data badge.
- Inspect the PCB coding / gas-group resistor.
- Repeat the gas-family check and enter the correct family. Combustion must be measured afterwards.
- If the resistor is wrong for the PCB spare, fit the correct resistor or the correct PCB kit.
Possible parts needed
- PCB coding / gas-group resistor for that spare PCB kit
- Boiler PCB kit (if the resistor is not available separately)
- Correct gas restrictor if the appliance was converted — also F.93