Responded to no-heat call for furnace that had been serviced previously. Diagnosed high pressure switch failure due to frozen intake pipe. Found exhaust and intake pipes terminating improperly in window well with missing elbow that customer had removed during summer renovation. Installed 12" pipe section with proper elbow configuration to prevent flue gas recirculation and intake freezing. Verified restored differential pressure readings and confirmed furnace now operating correctly with proper heat output.
