I got 2005 Malibu 3.5L v6 and when my AC is off the temp goes from 50% to 65% close to red zone which is 75% and above but the thing is when I turn on the AC it is like problem doesnt exist also when AC is off and it is overheated around 65% if I start driving around the temp goes back to normal. I checked the fans they work even when AC is off. Water pump and thermostat replaced coolant flushed 20k miles ago about a year or a year and a half ago with serpentine belt replacement.
If its not going into the red zone, it should be fine.The radiator fan should turn on to cool the engine when it reaches a certain temperature.Do you have unusual hot weather recently?
Sounds like the radiator fan isn’t coming on and when the A/C is on the condensor fan pulls enough air through the radiator that it helps cool the engine down
fans? you have 2? side by side? i changed the coolant on my 06 equinox and had the chance to see the fan come on while idling and using the bleed valve. i dont usually sit in the driveway and listen for the fans on/off so i assume they rarely run. i have never heard them running in the garage after i get home. and the equinox is known for somewhat odd behavior. electrical and such.