hot water only with central heating

[topbanana]

hello all. my father has been having trouble with his 'boulter camray 2' oil fired boiler.
he only gets hot water when central heating is on. it is a conventional system with hot water cylinder.
it recently occured on a combi boiler, where i was kindly given the advice that it was the diaphragm on the diverter valve, which i repaired. could this be the problem with his type of boiler?
i cant get down there for a while, but if i can sort out what could be the problem before going, or at least familiarise myself with possibilities, it would help me greatly.
thanks

 

[kevplumb]

FWIW i would be looking here

first

 

[topbanana]

spot on kev.
motor wasnt sounding when switching water on, and pump and boiler werent firing.
replaced motor on actuator, and that lovely sound of the boiler firing was music to my ears.
thanks again.