Boiler help

[davederby]

I have a glow worm 45 or 56 back boiler and co-ordinate "lfl" fire and I am having problems with my central heating.

The boiler works fine for the water comes on when the timer is set etc etc.

When is is on the heating and water the heating stays on for a while then it goes off and the pilot light goes off too so it then pumps the cold water round.

Has anyone any idea what it could be

Cheers

 

[adlplumbing]

could just be thermalcouple or safty device kicking in
when last time you had it serviced?

 

[davederby]

It was serviced a couple of years ago.

A bit more info on it:

When it is on water only it heats up then goes off then comes back on when needed and works fine.
When it is on heating and water it comes on stays on then when it goes off the whole lot goes off including the pilot light