Replacing Old Atwood AFMD35121 Furnace With Dometic Furnace In 2019 Keystone Cougar 5th Wheel RV

Published 08/22/2025

Question:

I’ve got a 2019 Keystone Cougar with a furnace that’s failing. The label says AFMD35121. Would the Dometic DMC74MRbe the right replacement, or do I need to cut anything to make it fit?

asked by: Harvey

Expert Reply:

Harvey, you’re right on target asking about sizing. The AFMD35121 was a 35k BTU unit that’s been discontinued. You can step into the 35K BTU # DMC74MR furnace by Dometic, but it is 2 inches taller than your current one. Most folks just enlarge the cabinet opening if need be, and you won't have any issue or difference from the outside since it uses the same standard size exhaust outlet.

Is this the original furnace that came in your 5th wheel RV?

expert reply by: Andrew N