Pilot light will not stay lit: the thermocouple and draught checks

A pilot light that will not stay lit explained in plain terms

The thermocouple generates a tiny electrical signal that holds the gas valve open once heated by the pilot flame; if that signal is weak, the valve closes the moment you let go, even though the pilot itself lit correctly. A draught across the pilot assembly, a pilot flame trimmed too small, or a build-up of dust on the thermocouple tip itself all reduce that signal in the same way. The thermocouple is a low-cost, routinely replaced part once confirmed as the cause.

Things worth knowing about a pilot light that will not stay lit

• A flame that dies as soon as you release the knob suggests the thermocouple
• The thermocouple signal weakens with age even without visible damage
• Draughts across the pilot assembly can blow a small flame out
• Dust or grime on the thermocouple tip reduces the signal it generates
• It is a low-cost, routinely replaced part once confirmed as the fault

Questions we get asked

Can I test the thermocouple myself?

Testing requires a multimeter and knowledge of expected readings — this is straightforward for a Gas Safe engineer during a routine visit.

Is a standing pilot outdated?

Many modern appliances use electronic ignition instead, but standing pilots are still fitted on some fires and remain safe when properly maintained.

Where we deal with this

• Melksham (SN12) · 12 mi
• Radstock (BA3) · 0 mi
• Westbury (Wiltshire) (BA13) · 13 mi
• Twerton (BA2) · 7 mi
• Nailsea (BS48) · 14 mi