have worcester 35cdi combi heating working but hot water is not the light is flashing fast book says air flow fault likely cause but how do i fix problem
Tricky one to pin down, could be fault with fan, aps, flue, harness or pcb.
You'd need to be au fait with a multimeter and frankly some of what needs checking is mains electricity - I wouldn't feel comfortable talking someone through it.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.