I have an old ac unit the fan turns on an I got air coming out of the vents but it is not cold air can someone help me please.

You need to see if the outside fan and the compresor are running if neither one its running, check to see if you have high voltage if you do, check the capacitor usually when they go bad they get swollen (they look like they are going to explode ) and also check to make sure you have low voltage coming in. If the outside fan doesn't run the compressor will over heat and shuttle off.