I have an old natural gas furnace. Model #: RGAA-080C Serial#: CN3D104 F4379 1895 . There is an electronic Air Cleaner where the return air comes into the furnace. The air cleaner is metal, with fins and wires, and has an "On - Off" switch on it. It also has, mounted to the furnace, a Cleveland Controls, Model AFS240Air Pressure Sensing Switch is a general
purpose proving switch designed for HVAC and Energy Management applications. It can be used to sense positive, negative, or differential air pressure. The light on the air cleaner does not come on when the switch is turned to on. Could the AFS Pressure Switch be bad? I believe the unit still works, if I can determine what part may be in need of repair or replacement. Any suggestions?