I have a Outdoor AC unit that has an A-coil in it, so it pushes all of the air from outside through huge duct work and into the ventilation, which by the time it gets to the last room its extremely weak.

But i also have a fan on my indoor furnace, but it's not hooked up to cooling, The indoor fan only kicks on when the thermostat sends its 24 volts to the fan relay

My question: Can i take the green wire from the furnace that normally goes to the thermostat and run it to the wall thermostat with the AC units green wire, so it gets a boots of air through the vents, or will i have to move the A-Coil into the furnace ?

1 Answer 1


In your case, the indoor fan should run with the A/C and yes the green wire should power the fan relay, as long as the discharge from the outdoor unit is tied to the return system. I looks like someone used a self-contained unit, usually installed in a mobile home instead of a unit that utilizes an "A" coil or slope coil mounted above the heating unit.

  • Also if I could I would move the A coil into the furnace. It's out of direct sunlight (radiant heat) and its closer to the cooling application. Oct 4, 2018 at 15:03
  • 1
    I do not know how you are going to remove the "A" coil from the outside unit and reinstall it in the furnace plenum. Good luck doing that. I would rather purchase a new A/C unit with a line set and "A" coil.
    – d.george
    Oct 5, 2018 at 10:58

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