Alright, so last summer, I noticed the A/C was being odd. It would only work for the first 30mins of driving, then the compressor would stop engaging, therfore, no more cool air. I was just thinking it was low on refrigerant, and it having 300,000miles on the charge, I just thought a recharge would fix. I evacuated the system and got it recharged properly at my boss' shop, using the right tools. However, the system works the same. For 30mins of driving, the A/C is ice cold, but after that, the compressor stops engaging and the air becomes hot. It will work again once it sits for a while, like overnight, but it will repeat it. Any idea what this could be?