had a similar issue in my car, turns out the interior temp sensor was unplugged, in my case it was a r32 and the centre console got removed and the sensonr never got hooked up, if there is no signal the aircon assumes the temp is -44 degrees and pumps in hot air to stop you dying...even if the thing is switched of, this really sucked in QLD in summer and i was so glad when i found such a simple fix!