We recently replaced our mercury furnace
thermastat with a digital one. Several days later
our fan began to run continuously whether the gas
heat was operating or not. It is an old furnace
with a ?'thermastat'? on the hot air side of the
furnace. It seems to have settings for on, off
and upper range for the heat.
When we first moved into this house I used that
thermostat? to extend the blowing time of the fan.
Now nothing. How do I fix the problem with the