Gas boiler pilot light won't stay lit

Murgatroyd

We have an old (10 - 15 years) gas boiler that's been working fine up until this evening, when the pilot light went out for no apparent reason. I've tried to light it several times but it just goes out again.

My knowledge of boilers is limited to say the least, so I'd be grateful if anybody could offer up any help. As the boiler is quite old, is the problem likely to be serious enough to require a new boiler? If so, how much (roughly, I understand figures may vary) would I expect to pay for one of these?

Thanks in advance for any help.

real1314

commenest cause of this is a duff thermocouple - it's a small pipe that bends under the heat of the pilot light to control the delivery of gas - if it doesn't bend, it shuts off the gas, normally this happens if the light goes out, hence preventing a gradual build up of un-burnt gas, in this case it's probably worn out.

iirc they're really cheap - sub £10, possibly sub £5, so it's just a fitting charge really.

Phone a local fitter and ask how much to fit a new thermocouple.

Murgatroyd

Thanks for the information, I'll give somebody a call tomorrow.

eco-friendly_2

if it doesn't bend, it shuts off the gas, normally this happens if the light goes out, hence preventing a gradual build up of un-burnt gas, in this case it's probably worn out.


Must make a note of that ! :T

red40

Yes it most probably the thermocouple, but just to correct real1314 and the operation of a thermocouple, it has nothing to do with bending metals it might if it was a very old oven.

But a thermocouple works by 2 disimilar metals, which when heated (pilot flame) creates about 30mv, this then charges an electro magnet inside the gas valve (waits for demand from hot water or heating), once demand is present the main burner will light.

So a thermocouple is operated by a small electrical charge

mrs_baggins

this happens to me all the time. I had a new thermocouple thingy relaced 2 years ago and all was fine for a while now the same thing keeps happenning again. Mind you its 16 years old so guess its fairly old for a boiler! wasnt happy when I had a freezing cold shower last night!

coolagarry

Murgatroyd wrote: »

As the boiler is quite old, is the problem likely to be serious enough to require a new boiler? If so, how much (roughly, I understand figures may vary) would I expect to pay for one of these?

Thanks in advance for any help.

I was having problems for years with an old boiler and decided to have it replaced with a Valliant EcoTec Plus wall mounted boiler. I'm really pleased that I replaced it and wish I had done so years sooner. It cost me nearly £2000 but that included extra piping from a difficult source to bring my whole system up to date. I'm sure you could get it done for just over £1000
Its a condensing boiler which is more environmentally friendly and uses a lot less gas so I should save the cost if I live another 50yrs!!

Claire_Jones_3

We had similar problem and the pilot light itself had burnt away to practically nothing so wouldn't hold the flame. Fortunately my friend is a plumber so managed to replace the part within about 15mins! All it cost me was some beer!

Murgatroyd

Thanks for all the replies. Hopefully it will just need a replacement part and not a new boiler.

daveyjp

Thermocouple may be ok. Get the jet of the pilot light cleaned, it gets bunged with carbon deposits over time.