I've got an '05 X sedan with 67k miles. It's fairly original, I haven't done many repairs as it's not been needed but it recently started overheating.

Traced the overheating to a bad thermostat. Replaced that and flushed the fluid. Used a no spill radiator kit to run it and burp most of the air, then confirmed it's full at the rear check point. All seemed well until it started getting hot outside. Now it starts to overheat and boil into the overflow when idling with the A/C on. The temps come down quickly if I turn on the heat and get the car moving, but today it was only upper 80's outside and it started to overheat in traffic.

I'm now a bit over my head diagnosing and could use some help. I suppose I need to pressure test the cooling system?

I also noticed that I only ever see one of the two fans running. I've got two electric fans, have only seen the passenger side running. Is there a way to test the switch that turns on the second fan?

Thanks.