Boiler with fire front installed 1974. Worked perfactly so far, now every thing, including the pilot light, cuts out after 25 seconds when the boiler is switced on. Pilot light can be relighted but goes out with a click a few seconds after the boiler comes on, shutting the boiler and the fire front as well, leaving us with no heating.
The system has been serviced but not regularly.
Can you help?

Israr Kureishy, January 2007

we had this happen to ours it was the thermocouple

michelle [stourbridge], April 2009

Check the thermocouple, which is in the flame of the pilot light.
It is an electrical device which signals the gas valve to shut in the absense of pilot flame.
It will have the appearance of thin copper tube, held with a clip at the flame end and a nut securing it to the gas valve.
You can purchase a universal thermocouple for a few pounds from some DIY stores and any heating supply merchant.

Pete., January 2007