Boiler & Pilot light

[Scoobmeister]

The pilot light does not light when the thermostat shows the heating should be on. Then mysteriously it may work 5 hours later.

The heating is not set on a timer and is on permanently

[gucciman]

what make and model of boiler is it. is it electronic ignition?
are you turning your heating on and off as you need it with the thermostat?

[Scoobmeister]

It is a potterton boiler, not sure if it is an electric ignition. We adjust the temp on the thermostat as and when needed, but when it shoud be working the pilot light does not light, but you can hear the boiler working

[gucciman]

well from your description it must be electronic ignition otherwise it would have a permanent pilot light.
could be a circuit board problem, or thespark generator, the spark electrode, the pilot head or tube cold be blocked, could be the fan at fault or a sticking air pressure switch. you really need to call someone out to take a look

[gasman]

Make sure the thermostat on the boiler is turned up to max as this could be overiding the room/wall thermostat thus only allowing the boiler to fire when the temperature of the system has dropped usually hrs after the room stat has called for heat. If that does not cure it then you need to call a Gasman.