I have a 20 year old payne heater with a similar age Honeywell thermostat...

The heater works when I put the thermostat to Heat. But when I put the right side switch to off, and then try to turn on the fan with the Left switch(ON-OFF-AUTO), moved from off to ON), the fan does not go on.

The thermostat 'G' terminal(blue wire) is connected but in the furnace on the circuit board, the control wire(blue) is not connected.

If I want the fan to work in the ON switch position, do I just connect this wire up to the GC terminal? Is GC notation the same as G? I think GC mean Green cool....but I need to make sure I'm connecting the right wires.