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

The rear pin is the PUMP PROVING MICROSWITCH
Which will always move for heating & hot water

The front one is the DHW MICROSWITCH
Which should only work for hot water

Asbestos, August 2017

More searching throws up some suggestionbs:

http://www.ultimatehandyman.co.uk/forum1/baxi-combi-105e-water-only-on-but-rads-get-warm-t49846.html

http://community.screwfix.com/threads/combi-boiler-heating-rads-when-on-water-only.134087/

http://www.urbanplumbers.co.uk/baxi-105e-instant-hot-water-problems-boiler-repair-blog/

https://www.superwarm.co.uk/5-common-faults-of-a-baxi-boiler-and-how-to-fix-them/

You will doubtless have already seen much info like this with your own Google searches. It may be more fruitful to post in a dedicated plumbing/heating/boiler forum than on a general purpose site like this one.

acp, July 2017

Thanks for the response, however these do not really answer the question, I have replaced both the diaphragms in the diverter, and the pins move out smoothly, the question is - when the system is calling for hot water only should both the pins (hot water and CH)on the diverter be moving out and engaging the microswitches, or should only the hot water pin be moving?
Thanks

nigel56, July 2017

https://www.avforums.com/threads/baxi-boiler-problem.939326/

https://www.diynot.com/diy/threads/baxi-105e-when-switched-to-hot-water-only-heating-turns-on.182099/

acp, July 2017