Question about central heat & air system?

The reason you are experiencing this is because your system is not balanced, You have too much cooled or heated air going into one room and not enough in another, you will need to call a HVAC Certified technician who will come out with the proper tools to properly balance you system by the proper amount of air needed for that room based of a verity of things, Sq Ft of the room, Any windows, Doors etc. You may try to do this yourself by closing the dampers on the registers but you more then likely will have the same problem unless it is properly balanced.

There should be dampers in the duct that can be adjusted. If not, you can buy them at Home Depot and install them. They are easy to install as you only need to drill about a 1/8" hole for them. However, you will need to take the supply ducts apart to do this. I am assuming you have round supply ducts that branch off of the main trunk. You can close the damper partially to the hot room and leave it wide open for the cold ones. Also, make sure the return ducts are open for the cold rooms as there must be a way for the air to return to the furnace. The hot air won't go in if there is no way for it to get out. Another thing to look at is cold air infiltration into the rooms through doors and windows. Use a candle around window and door joints to check for this. You may need to buy plastic window seal kits and/or install better weather stripping by the doors. Sometimes too much cold air infiltration won't be overcome by the hot furnace air. If this doesn't help, I would take the branch ducts off of the main trunk and see how much air flows. Then you would know if there was a blockage in the main duct. Use a vacuum to clean it out and do the same with the branch tubes. They usually never get that bad but if a home had lots of shedding pets it is possible.

Somehow your ducts are clogged or blocked. Check the cold rooms to see if you have closed the registers (duct outlets). If the house is new and this problem has always been, then the duct system was poorly designed. Make the builder fix it. If you had work on your furnace or duct work, the repair company is responsible. It is also possible that once branch of your duct work is broken allowing the hot air to escape into the attic for example. Something stored in the attic could have fallen and crushed a duct (crimped it closed).

Most hot air registers can be adjusted to restrict the air flow into rooms that typically get too hot. This generally works well if doors to the affected rooms are not closed, or if there is adequate air space under the door (or individual returns in the closed rooms).

The only consideration is that the majority of the registers should be fully open or at least not closed significantly (only restrict the hottest rooms). If too many of them are closed or restricted, there won't be enough air flow through the furnace and that can cause it to overheat.

Have your duct work checked meanwhile partially close the register in the hot/cold room. Internal fans can be added to push the hot/cold air to areas that need it.

I thought that's what insurance was for but I just got a bid for CA installation because I already have the furnace and duct work. $3495.00. I'm going to get a couple of more etimates. I live in PA near Pittsburgh. My son had a new furnace, Central air and all of the duct work done in Pittsburgh for $7,000.00

My neighbor experienced this several years ago. Some duct work came loose and the other parts of the house were not getting any heat..

Check the duct work for loose connections, disconnections, or leaks. Does the duct work need to be insulated?