On Feb 10, 3:32*pm, "Bob M." wrote:
wrote in message

...

After doing some digging around it would seem that some furnaces have
two modes...Fan "On" and "Auto". Theres no mention of it in the
furnace manual but Im starting to suspect my furnace has this option
that can be set from the thermostat. The problem is my thermostat is
one of those old kind with the mercury tube in it. No fan settings.
Maybe the previous owner upgraded the furnace but not the thermostat.
There's only two wires travelling from the furnace to the thermostat
so even if I had a newer thermostat with a fan setting, there arent an
fan wires to connect it too. Is it possible my furnace is stuck in
"ON" mode?

Replace the thermostat. *Get an electronic "set-back" t-stat, it not only
has the on/auto switch, but can be programmed as well.

Since he stated that he only has two wires going to his existing
thermostat, just changing the thermostat isn't going to let him
control the fan. He would also need to run additional wire connected
to the furnace to allow fan control.