I am renting a house and when the air runs it cools the downstairs almost too well. The vents are in the floor and the downstairs stays very cold. The upstairs stays very hot like there is no air up there. The vents are in the ceiling there and there is no temperature change there when the air is running. Is there anything we can do to divert the air to the upstairs? Could it be a problem with the system, do we need to have it looked at?

Can you feel any air moving from the registers upstairs?

I am renting a house and when the air runs it cools the downstairs almost too well. The vents are in the floor and the downstairs stays very cold. The upstairs stays very hot like there is no air up there. The vents are in the ceiling there and there is no temperature change there when the air is running. Is there anything we can do to divert the air to the upstairs? Could it be a problem with the system, do we need to have it looked at?
you do feel the air move but I guess it isn't enough to cool the room

This is a pretty common problem. This being a rental house,I think the best thing for you to do is to install a window unit. I doubt the landlord will be interested in zoning, or intalling a system upstairs. You might check around the furnace to see if there is a damper in the ductwork feeding the upstairs. Also, check the filter.