There are a number of ways to reset the system. First turn it off in the trunk, then turn the key on, and then turn the system back on. Get into the car, shift to drive while holding the brake. Now shift to park, and unlock the doors and get out of the car. With the drivers door open, go around the car and open the passengers door and then close it. If at any point you hear the compressor come on then the system is operating and the light should go out. Otherwise you may need to check with a shop that has the Ford NGS or IDS scan tools to see if there is a problem.