Was driving on a long trip with extremely high outside temperatures (110 to 115). The A/C was working great - keeping the car cool without being on the highest settling. I stopped for fuel and shut the engine off for the few minutes it took to do this. When I started the car again the A/C did not work. No noise or other indication of a problem. When I switch to max A/C the radiator fan immediatly speeds up making me believe the controls are sending the signals to the unit (as opposed to some control fault). Anybody else have this happen? Any insights would be helpful. Thanks. BTW - the car is a 2013 Cayenne diesel with 148K miles on it. THANKS!