Is the e-fan running when you turn on the A/C? That happened to me, my truck ran hotter when idling in traffic. Turned out the e-fan was unplugged. If your e-fan will not run, unplug it and jump fused power and a ground to it, if it still won't run then the fan motor is probably bad. If it runs with jumped power and ground, then you may have a bad fan relay or may have a bad coolant temperature sensor.

Jimmy

 

Clogged radiator?

 

That sounds like the problem I had last year. Check you e-fan first (by jumping it as 01SilverCC mentioned) then change out your coolant temp sensor and thermostat (just because these are relatively easy and cheap to do so that you can rule them out as possible problems). I did all of these as well as change out the fan clutch (which was bad, also a b***h to change!), but in the end my problem ended up being the water pump. It did not weep or make any sounds, it was just bad. As soon as I changed it out my truck cooled just as it is designed to do, and now I even run without my mech fan.

 

I recently fitted an aftermarket fan clutch as I had noticed a intermittent squeak coming from the front of the engine when starting from cold. I checked the fan and found about 1/4" of play when moving it back and forth.
New clutch has cured the play and the squeak, it has also noticeably reduced the normal running temp of the engine. I've got a 180 stat and have had the cut in temp of the efan matched in my HemiFever tune. In traffic, the efan used to cut in quite often but now it almost never comes on, it sits right on 180 all the time. You can hear the mechanical drawing air at idle but it immediately disengages as soon as you rev it. the only time the efan comes on is when you hit traffic after coming off the highway or when you have the A/C on.
I think its safe to say the old fan clutch was shot, even though there were no leaks from it. Car had done around 110K when I changed it.

 

Check to see if your fan is not put on backwards.