In the summer, you would want the air from the evaporative cooler going to
the ducts, but not into the furnace. So sometimes there is a way to keep the
evaporative air from coming "down" and going into the furnace.

In the winter, you would want the air from the furnace going to the ducts,
but not up and to the outside via the evaporative cooler. So you would want
to close off the duct from the evaporative cooler to your house ducts.

So see where exactly this open/close damper is located. Also see if there is
another on the roof. So you might have...

-Evaporative cooler on roof-
-Damper- (open in summer, closed in winter)
-Ducts and house vents-
-Damper- (open in winter, closed in summer)
-Furnace-

"Rick" wrote in message
Hi all,

Need some advice. I live in the southwest area(El Paso) and have
turned my gas fired furnace on. I cool my house with and evaporative
cooler located on the roof. When I shut down the cooler and fire up
the heater I have to open/close a flapper vent located above the
furnace. My question is: Is this vent suppose to be open or closed
during furnace operations?

TIA