Pontiac G6, 2008 about 48,000. AC won't start in the morning. It takes about 5 to 10 minutes on the road. Once ON, works fine all day. Next day, same problem. Sometimes I get it to about 4000 RPM for about 10 seconds, and the AC comes ON. Took it to the GM delearship, they can't find any problem, freon level is OK, and the AC works all day. next day, same problem. Any idea?