2000 Sable air conditioning issue


I have a 2000 sable wagon 76000 miles and for the past few years the ac has been working sporadically. On a hot day, if the car sits in the sun, when I start it the ac will blow hot air at full blast. When this happens I can’t turn it off or anything else in the instrument cluster(the radio). Even if I shut the ac off, hot hot air still blows out. Sometimes the radio will shut off and other times it will stay on but none of the controls work, I can’t change the station or volume level. THe dealer has replaced the entire dashboard unit which houses the radio and ac controls and replaced several sensors - over a $1000 later, I still have the same problem on hot hot days. If I park the car in the shade and let it cool down, the ac will then work. It drives me crazy, so my kid said “Ask the cartalk guys - they will know what to do”