a/c heater control switch

[4runnn]

I have a 94 runner,can someone please tell me what kind of problem i'm having, my a/c heat control switch does nothing when I turn it on. I have replaced the switch but no change

 

[wolfgang]

Low or no freon in the system. There is a low pressure switch which senses pressure and prevents the system from coming on. Had same problem in my '90 and it turned out it was caused by a corroded AC expansion valve which ended up being covered by a special service campaign and was fixed for free (this was just few years ago). Check to see if '94 was covered by that SSC P01 campaign.