Join Date: Nov 2008
Location: Rochester, Michigan
Using a single relay as in the last schematic, come off of the 85 relay terminal to the arm of a SPDT switch (which has a center "off" position). Wire one side of the SPDT switch directly to ground and the other side of the SPDT switch to ground via the thermostat. In one position, the fan will come on; in the other position, the fan will be controlled by the thermostat; and in the center position, the fan will always be off.