Baxi Bermuda firing up when CH/HW switched off

[vichighrise]

I'm hoping to pick the brains of the Baxi enthusiasts in this forum...

Recently moved into a property where the Baxi Bermuda (15 years old)
was firing up even when the CH/HW was switched off and overheating the
hot water in the cylinder.

British Gas checked it out, replaced the ACL Synchron Motor and
cleaned the Baxi at the start of the week but the boiler is still
firing up even when the CH/HW is switched off (although the HW
cylinder appears to be okay)

Is this normal, or should I be on the phone to BG again?

 

[gas4you]

I would have replaced the valve head and not just the motor. It sounds like the microswitch has broken and stuck on, nothing to do with the motor.

Can't see why this should make it overheat though as boiler stat should turn it off before it gets too hot.

Perhaps boiler stat needs checking as well.