I have a 2013 Acadia Slt-1 with 169+++ miles on it. Temp gauge starts to climb when idle like when waiting in line at a drive-thru when it's about 70 to 100° weather. Gets hot after A/C running for about 45 minutes but only when it's idle. Once going down the highway the temp goes back to normal. Any suggestions on where I should start troubleshooting? Thermostat, radiator, fans etc.