Here are two pics of the furnace controls
Pic 1 shows something that looks like at temperature sensor.
Pic 3 is the works. Along with something that looks like a pressure sensor, there is ther relay box. When I switch the fan off and on with the stat upstairs, you hear a realy click in the unit.
Everything works fine except the delay fan operation. It never engages. The fan is now set to run continously to procect the firebox.
I suspect the device shown in pic 1. Ideas? Hell I could replace all the parts for what service would charge me.