Boiler won't stay lit...please help

[kp7722]

Hi,

I have a 30(?) year old Glow-Worm Space Saver 38 boiler which, for the last 10 months (when I moved in) has been totally fine. With all the strong wind recently I've noticed that the pilot light has gone out a lot but I've always been able to relight it and carry on as normal.

Last Thursday I got home from work to notice that it had gone out again. I tried to relight it and it wouldn't. When I eventually did and turned the gas flow upto full (On) the whole lot just went out after about 10 seconds. I thought it was the wind again so I tried a couple more times without success and left it for the evening.

Over the weekend the wind was a lot more settled so I tried it again but still had issues. It doesn't seem to like a sudden burst of gas (i.e. turning it upto full quickly) - turning it from pilot to full will almost guarantee it going out. The only was I can get it to light is the following:

1. Hold down the gas flow dial and light the pilot.
2. After about 30 seconds I SLOWLY release the gas flow dial and pilot light seems to stay lit.
3. I turn the gas flow upto about a third, just to get the main burner to kick in.
4. Leave it for five minutes (which seems to warm it up and make it stable) and then turn it upto about two thirds.
5. Leave it for another five minutes and then turn it upto full (On).

This method seems to work but after I turn the heating off the boiler obviously cools down and then the pilot light will eventually go out (within 20-30 mins). This means I cannot set the heating to come on with the timer.

It's almost like the boiler doesn't like being cool? When hot, the flame seems stable even when cutting out between main burner bursts.

I do intend on getting a gas man out asap to take a look at it, but I just wanted a "second opinion" from you guys just so I know what to expect to be told. Could it be the thermocouple, or something more drastic? (the thermocouple also seems to lead up behind the boiler making it hard to change - is it a boiler off-the-wall jobby?)

Cheers guys, Paul.

[Pete Smith]

Go for a thermocouple, about a fiver for the part and 10 mins to fit. I had a 30 year old back boiler behind a gas fire that did exactly the same. Whatever you do, don't call BG or they will want to fit a new heating system. It's the equivalent of having a bulb changed at a quick fitting garage only to find you need shock absorbers, brakes, tyres and a finance deal!

[Andrew Gabriel]

Might be the thermocouple or that the pilot jet is partially blocked with dirt because the boiler needs servicing. When was it last serviced?

[Maris]

I had a similar problem. I suspected that it might be a broken sight glass, leading to a through draught through the boiler. Managed to secure a replacement for the very old Ideal Standard boiler (later IS boilers have similar sight glasses) and the boiler has not gone out since.

Maris

[Roger Mills]

For whatever reason, the gas valve is failing to respond to a signal from the thermocouple that the pilot light is alive and well. This can be due to any of 3 reasons:

• Duff gas valve

• Duff thermocouple

• Pilot not heating the thermocouple properly

This last one can be due to the pilot not being strong enough, or pointing in the wrong direction - maybe because of a bit of crud across the jet. The fact that it goes out with the slightest gust of wind suggests that you need to turn the wick up a bit. Is there a separate little governor which controls the pressure to the pilot - and hence the height of the flame? If so, tweak it up a bit, and make sure that the flame is directed straight at the thermocouple. If that doesn't work, replace the thermocouple. If *that* doesn't work, it could be that the gas valve is duff - but that's less likely than the other things.

[kp7722]

Cheers guys. After reading on the internet it did seem to be to be the thermocouple as the most likely cause. I get the impression that they are fairly straightforward to change/fit. When I look at my boiler controls I have the thermostat on the left, the ignition next to it, then the gas valve. Just to the right of the gas valve is what I think is the thermocouple (piccie from internet->

just above the right contact in the blue plastic part) - something that looks screwed into gas valve housing - with a copper pipe coming out of it, going under the boiler and then goes into the back of the boiler. Am I correct? If so, how do I disconnect/connect the back part as there doesn't look to be enough room! (couple of centimetres).

Is it a DIY job - I am a competent DIYer but I won't mess with what experts and professionals get trained to do!

Cheers, Paul.

[Mark Hewitt]

EEsh I remember having to go through that crap. And forever having to change the thermocouples!