No pressure when removing radiator cap

What is your question?

I have this 96 3.3 pathfinder with a new timing belt, new thermostat, new radiator cap. Now the vehicle doesn’t overheat while idling Or driving, it starts overheating the moment you turn the ac on and you are sitting in traffic, the temperature starts rising slowly. This is going to sound stupid, but I got out and removed the radiator cap and there was no pressure, no bubbling. the coolant is topped off and there are no visible leak, no burning coolant.

What makes this problem better or worse?

Better when the ac is off

How long has your 1996 Nissan Pathfinder had this problem?

2 days ago