worcester 28si ii, heating not working but hot water still works?

Maybe faulty controls including the pump, as its a combi and HW not affected, or faulty PCB or other controls in the boiler. Sorry probably not told you much more than you know already. Give Worcester Bosch (08705 266241) a ring as they're usually very helpful and those Greenstar Si Combi boilers are usually very reliable.

Stephen
March 2009