My furnace does not light up but we hear a clicking sound and the light indicaticator flashes three times anyone could help...
Flash guide says Pressure Swith Stuck Open?

There is a pressure switch on the plenum, connected to the inducer fan. It has to be closed to start ignition. This is a DIY job, if you know how to check and or clean the small ports. Might be worth a service call if you are not sure of what you are doing.