On Wed, 04 Nov 2009 12:20:37 -0800, mkirsch1 wrote:
The air coming out of the vents is cool, around 70 degreees according
to my thermometer. The exhaust to the chimney is smokin' hot. The
plenum does not get perceptibly warm.

Can you get a thermometer into the plenum at all and check there (or at
least whatever register's closest to the plenum)? Our system loses an
insane amount of heat in the ductwork and there's about 40 degrees
difference between the register nearest the furnace and the one furthest
away (I did post actual numbers the other week, but can't remember what
thread that was in, and I don't have them written down)

Never tested the exhaust temp on ours. Maybe they always run hot at that
point.

Just wondering if your problem's the furnace or the ductwork...