New to fords and all the quirks but Ill bet your 4x4 wont kick in without locking in the hubs also, if so check the connections on the solenoid and make sure all vacuum lines are intact thinking its located on one of the finders. This fixes it in most cases. My truck ac is really bothering me, I just don’t think it gets cool enough, but ill put some gauges on it this week and find out the details.