Heater not working

It first started a few months ago my blower actuator made the clicking noise so I took it into the shop and they replaced my blower actuator motor and it worked fine. Then my A/C would work but it would not switch over to heat. So I took it back into the shop and they put another blower actuator motor in it again and still the same thing. So then the mechanic thought the arm to switch the door from hot to cold was broken. Well, he tore it apart again and replaced the arm and another blower motor and after he put it back together I had heat but no A/C. Anybody else had these problem with the Nissan Titans?