Boiler will not fire

It is an old Radiation (Glow-Worm) Fuelsaver 12 RS which has worked perfectly for many many years (including this morning) but this evening I returned to find the pump running but the radiators cold.

The pilot light was lit but the boiler wasn't firing.

I cycled the electricity. Pressed the green reset button on the O/H stat and re-lit the pilot light but it still doesn't want to fire.

When you turn the thermostat knob from the off position you can hear a 'click' from that area. (But it does this when there is no demand for CH/HW too)

For the pilot light to stay on I believe that must mean that the thermocouple and the O/H stat must be working?

So I believe (from reading this forum) that the most likely candidates are the main thermostat, the solenoid or the Gas Valve?

Is there anything electrical I can check with a multimeter before paying £££'s to have it diagnosed and repaired professionally?

There is quite a bit that you can measure.

Voltage on gas valve solenoid. If nothing then check back to see where its gone!

If there is voltage but the gas valve is not opening then you could isolate and measure solenoid resistance. If its o/c then it means a new gas valve fitted by a registered gas engineer.

Tony

There was no voltage on the gas valve solenoid (the two orange wires) so (after switching off the power) I removed the screws that held on the metal enclosure holding the electronics and transformer. Re-wired everything and I now read 24v AC and the boiler fires up. It appears fixed.

Might have been a loose connection.

Simple really!

Tony