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Ask Andrew Smith Your Own Question
Andrew Smith
Andrew Smith, HVAC Technician
Category: HVAC
Satisfied Customers: 3629
Experience:  Heating and Controls engineer
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Could a faulty microswitch in the mid position valve cause

Customer Question

Could a faulty microswitch in the mid position valve cause boiler not to fire up?
Submitted: 3 years ago.
Category: HVAC
Expert:  Andrew Smith replied 3 years ago.

Andrew Smith :

Yes, if the valve does not open fully and engage the microswitch then the boiler will not fire

Andrew Smith :

If the valve does not open fully when on hot water only the boiler may not fire

Andrew Smith :

Try this;

Full Size Image

Andrew Smith :

Follow the live backwards from the boiler, you could use a link between the live and boiler live and see if it fires

JACUSTOMER-w2863zud- :

Thanks Andrew, will try and get back to you.

Andrew Smith :

How did you get on?

JACUSTOMER-w2863zud- :

Tried it and no luck. Even the Red live from controller to Red to boiler? I know the gas valve makes a noise when shutting off, but is it possible the valve at the solenoid end is faulty? All this from a blown fuse??? Lot of people confused...

Andrew Smith :

It may have been the solenoid burning out that blew the fuse.