a little help

I have a 2007 Titan Crew. Intermittently when I switch front vent to defrost it will take 29 sec (yes I counted) to make the change. I stopped by my dealer when it was doing it and the service manager said that it is taking way to long (hey thanks). However, after they pulled the truck in, they shut it off and by the time the tech looked at it, the transfer returned to normal. At which i got the old "we checked the time compaired to another truck and your's is normal". At which I asked the manager if it was still taking as long when the tech checked it and he could not answer. It also seems that when I am having this problem (and this is the part that really gets me) it also takes a long time for the fan/AC to respond (delayed in the time that I crank the fan until it begins blowing). Any suggestions????