"Thanks for the reply. Sounds right on. I was just playing with the
Tstat. There is an adjustable arm behind the main control (this is the
round heat only style stat). After a few adjustments I think it will do
the trick. "
The fan control Greg was referring to is the limit switch on the
furnace, not the thermostat. The fan limit switch controls the temps
that the plenum must reach for the blower to turn on or off.
I guess it's also possible as you suggested that someone could have
moved the heat anticipator in the thermostat to an extreme setting.
That apparently is what you are fiddling with. It's function is to
introduce some small amount of heat to the thermostat so that it shuts
off a little before reaching the desired temp. That way the remaining
heat in the system brings the house to the set temp, not overshooting.
At an extreme setting, you might be able to set it so that it shuts
off the furnace before the blower can turn on, but I haven't seen that