"Mike S." wrote in message
The problem I have is that if I set the thermostat to to 70 degrees
fahrenheit, then the downstairs stays about 70. But the upstairs will
be anywhere from 76-80, depending on the room and how hot it is
outside. So the problem is that people complain that it's too cold
downstairs and too hot upstairs. Ideally, I would like it to be about
76-78 downstairs and about 74 upstairs.

Why does this happen and is it normal? I know that a lot of air blows
out in the vents downstairs and not a lot blows out upstairs. I shut
off all the vents that aren't needed and close the doors to rooms that
aren't used. I have the fan set to "auto". I don't know if leaving it
on auto is better than setting it to "on". I don't like to mess with
it because it seems to cause problems with it.

Any opinions or suggestions (other than buy a new unit)?


You need to balance the system better, but you are on the right track with
what you have been doing. . First, be sure all filters are clean, no ducts
shut off. Be sure the belt on the blower is not loose and slipping. Does it
have to be lubricated? Next, close or partially close the downstairs vents
as you have been doing to force more air upstairs. Check returns to see
that they are not blocked also.

During the day, the upstairs is subjected to much more heat from the sun on
the roof. You may bet better results if you vent the attic better and
perhaps add some insulation.

Turning the fan to the "on" position will make it run all the time. That
may help distribute the air more evenly, but at the cost of running the
blower all the time. Closing the doors to rooms not used may help or
hinder, depending on how well the air is flowing around the house.