Air con on passenger side has started blowing hot air for about 30 seconds some 15 minutes or so after starting engine. It will go on to blow out correct temperature air after that without further problems for that journey how ever long. Outside temp doesn't seem to make a difference. Mainly seems to come out of dash vents (both side and middle).

Main dealer seems to have no idea what is causing problem. I am reluctant to have the whole dashboard taken off as that could cause additional problems with new rattles & squeaks especially when fault cannot be accurately identified.

Anybody come across this before? Typically vehicle is just out of warranty!!