Sprinter Furnace Ducting

[Carr25]

Hello have an 353FWDEN. Recently started having issues with the propane furnace. Not sure exactly which suburban furnace it is but between the sf-20fq through sf-42fq. Issue is that the system is not blowing out of the vents. I checked at the furnace and system is blowing without issues. System is blowing air in the system but it's not even enough to lift a piece of paper. Ran an camera down the ducts and only found one spot at the end of the rear run that was crushed. This has three floor ducts on one run and three on the next run. So comes in and tees off going to the front and rear.

It appears the only way to get to the ducting is from the underbelly. Went to take this off and the cover is the full length and held in with nails with bolt heads.

Wondering if there is anything else to check on and any way to access these ducts?

[flybouy]

Curious how you checked "at the furnace". Did you remove the furnace and check the air flow?

[Carr25]

I didn't remove the furnace. I was able to take the cover off where it leads into the duct and it blows really good. With the vents off I can feel that it's pushing air through the ducts but just doesn't seem like it's enough.