Make sure both your cooling fans are working. The plugs going to the radiator fans commonly develop a weak connection which eventually causes the fans to not turn on when they should. This issue usually goes unnoticed until the engine overheats or the A/C doesn't work well at stops because the fans aren't turning on.

 

My 05 nox recently had a huge over heat issue.. everyone is telling me head gasket but I'd like to know more about the AC not working well at stops because my car has done that for a long time the AC blows cool while driving but if I stop it blows warm air same with the heater.. blows heat while driving but when I come to stop blows cool air. You're saying that that has something to do with the fans that cool the car??

 

It could. The radiator cooling fans run when the A/C is switched on to provide airflow through the condenser. If the fans aren't running, air will only flow through the condenser while the vehicle is moving. The A/C can't cool as much if no air is flowing through the condenser. If the fans are running fine you may have an issue with the compressor. The 2005 Equinox used a scroll type compressor with a control valve that commonly failed, so that could be your problem if the fans are running. The telltale sign of the control valve failing is no cold A/C at idle. The fix for that is to install Dorman p/n 917-275. Replacing this part will require you to evacuate and recharge the A/C refrigerant. A shop is usually willing to do this for you for $100 or less.

If the fans are not running, check the connectors going to them. They commonly develop a bad connection over time, and sometimes melt the connectors if neglected for too long.