940 Overheating with AC on in Traffic. HELP!

[whystore1]

Hello, I have a 1993 940 wagon with 66k. My problem is this... When I'm driving on the freeway under normal driving speeds, the AC works great, and blows around 40 degrees. When I'm in stop and go traffic with the AC on, the temp gets much warmer. Then, if I continue to leave on the AC, the car will start to overheat. So, it works fine when I'm driving along, but gets hot, (both air temp and car) when it's stop and go.
Last weekend I changed the thermostat, and flushed out the cooling system.
Any suggestions on how to keep my car cool?
I need some help!
Thanks,
Toby

[LaRy]

Check the fan. If it is a mechanical driven fan it should be blowing hard for one minute when starting the engine, after that the blowing should be reduced to almost nothing. Except from when the fan hub is getting hot from hot air coming from the radiator. Then the slipping should stop and a thermostatic function inside the hub should make the fan run at full capacity.