I have a Baxi 105e boiler, it has started to heat the radiators when the hot water tap is run. I've replaced the diaphragm in both the Hot water and Central heating diverter valves, and made sure that the switching pins run smoothly.

When I set Central heating only, the pin on the CH diverter switch moves out and switches the switch, and the Hot water one does not move ( as expected), However, when I demand hot water, the pins on both switches move out ?? is this correct?

Can you please advise, should both switches engage for hot water only, or should only the HW switch engage? Can you advise on likely causes and remedies.
Thanks in advance.

nigel56, July 2017