Help please! I would like to attach a lawn sprinkler irrigation timer
to my thermostat so that I can automatically run the fan (without a/c
or heat) for air circulation at various times of the day.

The reason for attempting to use an irrigation timer is that,
apparently, even if I upgrade to a digital/timer thermostat, I still
can't control the fan alone. (My current thermostat is an old-style
White-Rodgers.)

The irrigation timer outputs a 26v signal (which in normal usage goes
to a solenoid in a water line valve)....can I just run a wire from
this port and splice it into the green (fan) thermostat wire (which I
believe is 24v)?

And what about the 'common' connection? I certainly need to connect
the irrigation timer's com port to another colored wire coming out of
the thermostat. (I know nothing about wiring/electricity as you can
tell.)

Thanks in advance for any help and comments.