Toyota Repair: 2008 Rav4 AC, auto parts store, pressure gauge

Question
My air works fine until I stop in traffic -- while stopped for more than a minute or so it starts blowing warm air. As soon as I accelerate it blows cold again. I took it to Toyota dealership and they found nothing wrong with it. It happened again twice this week. I want to go in with an idea of what may be wrong for them to check it out. Frustrated - it's hot where I live and lots of traffic! :( the car has 71,000 miles

Answer
Hello,
The most likely cause is that the system is low an freon, I have no idea what they checked or they just told you there is nothing wrong without checking system freon pressures, it's obvious there is something wrong or you would not complain about it.
Here is what should be done when taking it in for a/c diagnosis:
Connect a oomputer controlled A/C service machine
Check the freon pressures
If too low, the system is evacuated and the correct amount of freon is put in
the system is retested and raod tested to confirm the problem is fixed
If for some reason the pressures are abnormal there would be additional diagnosing required
Please go a shop that has A/C expertise and qualified A/C tecnicians and explain the problem and make sure they test drive it after the repair so you don't get the car back with the same problem.
Here's what you can try yourself if you wish to do so.
Go to an auto parts store like Autozone and buy a A/C recharge kit, get the one that has a pressure gauge on it for about $35, follow the instructions that come with it and see if it will take some freon in.