"Chemqueries" wrote in message
...
When my furnace is on, there is cold air coming out of two large vents in
my
house while warm air is coming out of all the other heating vents. Is it
possible that the heating and air conditioning are on simultaneously? My
thermostat allows only for EITHER heat OR cooling. You can't turn on both
at
the same time. What is going on? By the way, I had the furnace cleaned
about 6
weeks ago.

Are you sure those "two large vents" aren't the return vents? (Some call
them cold air returns)

When the unit is running, take a paper towell and see if those two vents
will suck the towell up into them......