Well the A/C light flashing is indicating a fault in the A/C system. Usually (not always) that can be either a low charge, a seized compressor and/or an air conditioning clutch failing to engage/slipping.

You can verify this by having someone start the vehicle and push the A/C ON while you watch the compressor. You should be able to spin the clutch assembly (not the pully the belt runs on) by hand, if you can't the compressor might be seized. You can also watch the engagement of the clutch if you have someone turn the A/C ON while the vehicle is running, you should watch the clutch engage and spin the pulley with little to no slippage. If the pulley seems to slip or the pulley turns slowly the clutch is likely failed/failing.

Hopefully that's helpful.