Age of RHEEM furnace

[Michael_J.Shultz]

Model # is RGDA-100C-ER, Serial # is CN 3D104 M3688 5406. Please help

[lkage (Larry Kage, CMI)]

I’m looking for an “F” in the serial number…don’t see it where the “M” is but it is probably an '88.

[mhawley (Mathew Hawley)]

Ditto Larry, Looks like the 36th week of 1988

[rray (Russel Ray)]

Yep.