Good idea after giving the system a power flush fitting one will trap any bits and stop the boiler from getting blocked but it's a shame one wasn't fitted on installation. Bob
You need a good sparky who's well up with electronics to Id the fault then the engineer knows what he's got to do,I use one who diagnoses tricky faults for me saves a lot of time,I'm ok with most things but this guy sorts out the brain busters for me. Bob
Which lights are lit on the front could be you've low pressure which means the burner won't light till the pressures raised over 1 bar or it's on overheat which means it needs to be reset. Bob