Do you live on Venus?

 

I’m guessing there is trapped air in the system. The symptoms are running hot at idle, and the heater throws cold air; when you accelerate, the engine temperature drops and you get warm air from the heater.

To fix this, you open the air bleed in the radiator hose that is near the firewall while adding coolant.

--Spike

 

Having same problem as OP. Car runs fine without a/c no matter outside temp or speed. However when a/c is running and car stopped, it quickly overheats. Upon moving, temps immediately lower.

Both fans run, fluid levels ok.

Bad Thermostat?

 

Wait a sec, the fans are on but it still overheats? And when the car is in motion the temp is fine?

Try this: While the car is NOT in motion, fans on, car starting to overheat, rev the engine to about 3k and hold for 4 or 5 sec. See if temp shoots down.

If so thermostat could be stuck closed, and its needing the water pump at rpm to open it and circulate the water.