An HVAC contractor can install one condenser and then have separate evaporator coils in each room with a thermostat in each room.

A coil element can go bad and arc electrically.

No one knows how to clean the lint and dirt from the cooling coils.

And laying it on second floor over plywood is easy using a toe nailer. 

It taught me a few troubleshooting tips (I already knew how to clean coils and make sure drain lines were clean).Because of this I saved myself several service calls that would have involved a high priced tech replacing; thermostats, exhaust fans and relays.

You can see the homemade copper refrigerant condenser coil inside what's left of the PVC pipe which used to have water flowing through it to provide cooling. 

In three years, the washer has needed no service, and the dryer needed gas coils or something for a couple of hundred dollars. 

You have to clean out all of the Air vents (professionally) and maybe even your coil if it's dirty.Scrape any popcorn off the ceilings, and Kilz all the walls and ceilings.All the flooring has to go! 

Yes if it has central A/C definitely get the vents and ducts cleaned, as well as having the air handler serviced and coils cleaned. the tar gets on everything so it really is just wash down everything to the best you can prior to starting to repaint.

Strange analogy, but the furnace motors were overworking to keep a reduced return airflow flowing over the Evaporator Coil.