I recently bought my 16 y/o daughter a 79 F150 Supercab with a 400 and c6 auto tranny. The ac was present but low on freon, a friend added freon for me and it blew cold. Now off and on while driving the a/c system just quits for a time and then kicks back on. The blower fan and everything stops, any ideas?

 

Could be a couple things. Does the AC system totally shut off, fan not moving? That could be electrical. If the blower fan is moving but not blowing air then maybe the evaporator coils froze over and stopped the airflow. You may want to check that the condensation drain is not plugged too.

I'm no AC expert but know enough to get myself into trouble. At least this post will bump you back up.