F.32 displayed; fan does not run or runs erratically, no ignition

Safety: Isolate power and gas. The fan is part of the flue gas system; only trained personnel should service it.

• Access the fan: Remove the front cover and combustion chamber cover as per Vaillant instructions. Locate the flue fan assembly.
• Check for obstruction: Inspect the fan wheel for debris, soot, or foreign objects. Remove any obstruction and ensure the impeller spins freely by hand.
• Inspect wiring: Check the fan connector and harness for loose pins, burns, or damage. Reseat connectors firmly.
• Test fan operation: With appropriate safety measures, power the unit and observe if the fan starts when there is a demand. If the fan does not run or is noisy, replace the fan assembly.
• Check speed feedback: Some fans provide a tachometer signal to the PCB. If the fan runs but F.32 persists, the speed sensor or PCB may be faulty. Test according to Vaillant service data and replace the defective part.
• Reassemble and test: Ensure all seals and gaskets are correctly refitted to maintain flue integrity. Reset the appliance and confirm normal operation.