LF
Multiple causes
Could be
Ignition electrode 173528
Detection electrode 173529
Detection lead 173512
Spark generator 173538
Condensate trap 174244
Flueing issues
Gas supply problems
Wiring harness problems
Or maybe even the pcb
The list of possible causes for LF are numerous
& each one requires a different strategy to test it
The boiler manual goes into great detail as to how try to test each component
Provided you have a multimeter a flue gas analyser & a manometer
Q
September 2015