On 7/27/2017 13:54, Uncle Monster wrote:
On Thursday, July 27, 2017 at 3:46:15 PM UTC-5, Taxed and Spent wrote:
I have a thermostat that allows a setting for fan only, which I wish to
try to try to push some air around during the warm weather. There is no
AC. Furnace is 1960's vintage, and had only two wires to the
thermostat. I added a C wire for the smarter thermostat. If I add a
FAN wire, will the old furnace have a place to hook it up and respond
appropriately?


It should have. It's where the green wire hooks up. It will be marked with a "G" which is for the fan relay. ヽ(ヅ)ノ

https://highperformancehvac.com/ther...g-colors-code/

A 60s vintage furnace may not have a fan relay if the fan is controlled
by a thermostat in the heat exchanger. If that's the case you have two
choices: 1 - Add a line voltage switch across the fan thermostat and
control the fan locally, or 2 - add a fan relay with the contacts
shorting the fan thermostat.