The other day my ac started blowing hot air so I tried to add some freon. When I went to add the freon the meter on the can was in the red, between 100 and 150 psi. I'm not very familiar with ac systems so any info would be greatly appreciated.
Take it to a shop and have it done. Pending on the last time it was serviced, you could and proably have a leak. The lines need to be evacuated before they can add the refrigerant, and/or find said leak.