Ac blowing hot air

Hi, this is Dusty, I'm one of the auto experts on RepairPal's Car Genius team! That sounds annoying to me! It could be something as simple as the A/C compressor clutch relay is weak, not seated fully, or there's an issue with the connection in the fuse block, causing it to disengage after a bit of highway driving. You mentioned that the A/C works in the city just fine, this is likely because the A/C compressor is being cycled on and off repeatedly and the relay isn't required to hold engagement as long. There are other possibilities of course, but a first-hand diagnosis by a competent professional would be the best course of action. They'll be able to test all aspects of the HVAC system to make sure everything is in good working order, as well as pinpoint the culprit causing this issue. If you have any other questions or would like to help with finding a RepairPal Certified shop in your area, give us a call! 877-913-1554