After one hour the heater & air conditioning stops working ...the fans are still blowing nothing out of the vents no cool air or/ heat...no one can find the problem 3 mechanics. ...because it takes one hour for the problem to show up while I'm driving

the a/c compressor is either overcharged or undercharged,or the compressor clutch relay is sticking and running the compressor all the time,and the evaporator is most likely freezing up,then it thaws out after that hour and starts blowing again!!the relay is in under hood fuse box,marked with a snow flake! if it is undercharged,the compressor will run more often than it should and freeze the evaporator.check hepa filter behind glove box in blower box also,to see if dirty,or clogged.low side pressure should be 20-25 psi with compressor engaged..