VW Polo Air Con Problem?

[03Polo]

Hey Guys,

Our polo has been having issues with the air con whereby it will be blowing nice cool air and then randomly will start blowing hot air even though the dials were not touched.  If we switch the unit off and leave it for a few minutes and then turn it back on it reverts back to pumping cool air!  Has anyone come across this problem before???   Any ideas on the cause would be appreciated.