When it's 90+ out on the highway mine started blowing warm air for a minute or so and then back to cool. Has done it a few times now. I think I"m going to the dealer to check it out next week.
Go to this link and scroll down to the 2006 TSB section to find #24-012-05a. It will open up the PDF file showing the detailed TSB info. It may not apply to your vehicle but its a place to start.There is a tsb out on that problem. I believe all that is involved is a new scan