Before attempting to remove the furnace from its location, first remove the 'outside' furnace exhaust pipe assembly (4 screws) from the outside wall.
Once the furnace is re-installed, then re-install the exhaust pipe assembly.
Bob
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2016 GM 2500HD 6.0L/4.10
2018 Jay Flight 24RBS
2002 GM 2500HD 6.0L/4:10 (retired)
2005 Jayco Eagle 278FBS (retired)
1999 Jayco Eagle 246FB (retired)
Reese HP Dual Cam (Strait-Line)