I read some of the other similar posts. I am encouraged that there is a way to do without a spot for the green wire. Labman, could you give me directions on how you to accomplish this.

Thanks so much!
Nate

You will need to add a separate relay. Find a 4 wire one rated as high or higher than the blower motor with a 24 volt AC coil. For the line and load connections, link them to the same terminals as the original relay, one to the black feed wire from the house, and one to the lead to the motor. It should already be connected to the white house wire. Connect one coil terminal to the thermostat terminal the blue wire is connected to. Connect the other transformer terminal to one terminal of the new switch. Then run a wire from the second terminal on the switch to the second terminal on the new relay coil. With the switch in the on position, 24 volts can flow from the transformer to the switch, to the relay coil, through it, and back to the transformer. The relay contacts will close connecting the motor lead to the house wiring.

When you say "relay" are you referring to the fan limit or the device that controls the gas?
Thanks!
Nate

The relay is one more doodad. Follow the wires back from the blower motor. One should connect the white wire that comes in from the house wire. The other should go to a little box with 3 other wires, one the connecting to the black house wire. There will be 2 smaller ones, one to the limit switch, and one to the transformer. You need another relay like it. 3 of the wires you can connect jumpers from the existing relay. The fourth wire connects to your new switch instead of to the limit switch.

Fan only is a good deal. You can use it to circulate air to cool the house when it is warmer inside than outside.

I would like to see if running the fan alone actually works in distributing the heat. Couldn't I just wire the fan straight into the 110 to get it running and see how well it does? If it works well I would rewire the furnace.
Thanks!
Nate

Yes. You need to attend to wire sizes and the electrical code with 120 volts. You could also skip the relay and wire a suitable switch for the 120. If you don't locate the switch on the furnace, you would have to run 14-2 with ground NM or better to it. All 120 connections must be in a junction box.