11. Install the replacement pressure switch from this kit, On older model furnaces both of the mounting holes on the new pressure switch may not line up with the mounting holes for the removed switch. It may be necessary to drill a new mounting hole in the vest panel, being careful to not damage wiring, or other components in the vestibule or behind the vest panel (e.g. a heat exchange tube), 12. Reconnect the wires and tubing to the new pressure switch.