I own a 2002 Chevy Malibu, I have experienced at one point my A/C blowing only hot air then out of no where about an hour later it started working again. I never thought anything of the situation until I read the reviews listed on this site. Just recently I've became fed up with this vehicle. On Friday (today is Thursday) When I got off work my car would not start and the Anti Theft light was blinking. My car would not start for days I had it towed to the dealer on Monday in which it still wouldn't start. The dealer charged $60.00 for the tow and after missing 3 days of work I get my car back with a total charge of $150.00 for a radiator cap and coolant overflow bucket which has nothing to do with the car not starting. But if those items were not repaired I would have voided my warranty. Long story short. Nothing was detected in the exam of the car. The only they could say is that the Body Control Module within the Anti Theft System could be the case in which they have no equipment to assist with the possible problem. I am then told to not be surprised if I go to the store and my car not start when I come out. I HATE THIS CAR.
This car runs really nice, but the process of up keeping it sucks.
I would rather have something else.
The anti-theft ignition switch thingy is showing up as a problem on GM cars of this era and I think that is definitely your problem. You say you have a warranty? In that case, they should not charge you anything for these repairs and do not ever listen when they hold a $150 repair over your head by saying that not having it done will void your warranty, that is extortion. The radiator cap would not prevent the car from starting as you described, and it should not be worn out already given that our '98 Buick still has its original radiator cap.
This car is definately a piece of junk. I own a 2001 Malibu and it is terrible. Constant overflow issue and no one seems to know how to fix it. Got a new radiator cap, new thermostat, and lots of other new things. I just want this car to go away! I'm thinking of donating it to charity as they take ALL cars working or not. No more Chevys in my house EVER AGAIN!