On Saturday, 22 October 2016 15:44:04 UTC+1, kennygw wrote:

Hello I hope someone can help with this one.

I have an old Potterton fireside black beauty 35/51 back boiler.

until this morning it was running fine. It flamed up fine and the
heating/water came one fine. after it bit it turned itself off, and the pilot
light went out.

I turn the starter vale to off and left it to cool down.

when I went back to it to relight the pilot light after about 20 minuets. It
relight fine I turned the starter vale back to on. After about 20 seconds the
was a hissing sound then a clicking sound and the pilot light goes out.

I gave it all a good clean with vacuum cleaner and air duster.

It does the same, the pilot light come one fire time very time. The flame
look nice a blue and is one flame.

If I turn the heating and water on before I light the boiler it will flame up
fine and run okay for a bit.

It looking like it get to where it will flame down in normal operation then
after about 20 seconds it stars to hiss then the pilot light goes out.

Anyone got any idea what is up with it?

The pilot light needs to heat the thermocouple enough to keep the valve open that keeps the pilot flame on. The flame pointing bits or thermocouple may be out of position. If the TC is heated too much it gets red hot & doesn't last so well.

If the thermocouple is getting all the heat it can but it still doesn't work, time for a new thermocouple.


NT