Gas Safe Engineers will tell you to leave well alone and quote the regulations at you - it's either a case of job protection or inadequate understanding of the regulations.
The big sin is doing work (taking money) for repairing a boiler when you're not Gas Safe trained and registered - a very sensible thing.
The regulations also say that an unregistered person should not interrupt the gas-way without having a registered person check for safety afterwards.
The regulations also say that a user (you) can mess around with your own equipment as much as you want PROVIDING that you're not being paid to do it and that you do not interrupt a gasway. It says specifically as I recall that you can work on the controls.
Gas Safe Engineers will shout at me and tell me I'm wrong - many Gas Safe Engineers also guess what the problem is when working on a boiler - the word diagnosis is alien to them analytical trouble shooting a mystery.
http://www.legislation.gov.uk/uksi/1998/2451/contents/made
And anyway - if it is forbidden - who's to know?
2.6) Nothing in these Regulations shall apply in relation to—
(c)work in relation to a control device on a gas appliance if—
(i)the device is intended primarily for use by a consumer of gas; and
(ii)the work does not involve breaking into a gasway.
Good Luck..., August 2015
