Johnson & Starley warm air heating ?

Last Nov 2013 we had the circuit board changed on this warm air system because it was clicking constantly before the boiler fired up and continued this until we turned the system off. Now this clicking noise has returned but as well as that the boiler fires up then goes off, this is repeated within a matter of say 1 minute until the boiler finally stays on. We have to either turn the room thermometer realy low or really high to combat this. Please can you help?