Hot smell from AC

I have a 1995 Toyota Tercel. It has around 320k miles. Recently I have noticed an electrical hot smell that appears to be coming from the AC when it is idleing, like at a redlight. When I continue down the road, the smell disapates. I never smell it when traveling at highway speeds and only occasionally when stopped at a redlight. I replaced the fan resistor but it made no difference. Anyone have any ideas?
Thanks,
David