my air condiction works fine bu when i put it on heat it wont come on at all no fan no noise or anything only thig i hear is a clicking on the circuit board that's it i have a lennox furnace
thanks in advance

If this is an electric furnace then your contactor switch has gone bad and needs replaced. Call a service person to do this. Working with high voltage electrical current is not smart if you are an amateur. Refrigs are ok, but furnaces, no.