I have an old Glow Worm Space Saver 50b boiler which works ok when heating the water, pilot lights runs, main burner come on and off all just OK. However when switching on the Central Heating the main burners run for 6 secs then there is a loud 'solenoid' click and both the maina burners and the pilot light are extinguished. The pilot light can be re-lit manually and runs perfectly well afterwards. I'm assuming from that the thermo coupling is OK. Any ideas?
Ty running the boiler on heating with the boiler thermostat at the lowest setting and see if it stays on, it could be overheating on central heating mode