My 10 y.old Thermocompact 624e is refusing to start. I keep getting code F 1 on display, then it tries to start and then F 1 again, sometimes I get F24. On very odd occasions it has managed to start but not for long. My plumber has replaced the pump but is now stumped.

Dave, April 2016

This may help:

http://www.villageheating.co.uk/news/vaillant-boiler-error-codes-explained-infographic/

F1 = NTC Fault
F24 = Pump not running/blockage (Not necessarily in the pump, remember!)

XXX, April 2016