My S420 AC sometimes on very hot days, ( F 100+), will cool fine and then after sitting in a parking lot perhaps 30 minutes will not resume cooling. Upon re-starting the fan will blow like normal but it creates NO cooling of the air. It's as if I had pressed the EC button !

Do you have a possible explanation for what might be causing this. Later the cooling comes back normally.

Is there some device or switch which will disable the compressor under very hot underhood, or in cabin air temps?

I want to have a good idea about what exactly is going wrong before I call the MB dealer, (who for a few more months should honor the "Starmark" Warranty).

DanielW