Intermittent A/C cooling

This sounds like it is low on Freon. Let's run through this guide on how to check the pressures and then evacuate and recharge the system. This will tell us if we have a leak as it won't hold a vacuum.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

If we are low and no leak then we need to charge it back and retest the operation of it. Also, we need to check pressures to make sure the compressor and other components in the system are working.

https://www.2carpros.com/articles/air-conditioner-how-to-add-freon

Once we get this info, we will either fix the issue or know what is wrong with it. Let us know what you find and we can go from there. Thanks

Okay. That is great info. Thanks for that. Then that leaves us with air flow over the condenser. I didn't go here because you said both fans are working but if the A/C is working properly when moving and not when sitting still then the Freon is not getting cooled enough when you are not moving. That is the only variable when you are moving versus not moving.

The only thing in the system that "knows" you are moving is the amount of air flow over the condenser. Otherwise the system all works exactly the same whether you are sitting still or moving down the road. Again, this points to an air flow issue. Are you able to confirm the fans are coming on high? You should have two fans that have two speeds. Take a look at the wiring diagram for the relays. I would suggest we remove both relays and jump them both so that the fans come on high.

Let me know that the fans go to high speed.