During idle at a redlight, I could normally feel that the car was on. Now at idle while stopped, it seems like a fan shuts off... I can tell because the car would suddenly run very smooth when the fan kicked off. It would make me think my car died until confirming it was still on by looking at rpms.... then the A/C gets warm.
When I start driving again, the A/C will return to normal and become cold again.
My car will drop in rpms and suddenly die sometimes when coming to a stop. No bad noises, no clicks or put-puts... it just gets weak and shuts off. This only started happening with the A/C issue. Maybe they are related?
Regarding the A/C, I had the same issues a few months ago. Only ambient temperature air would blow through the vents while at a stoplight, but cool air would blow through the vents while the car was at speed.
For me, the accessory fan shorted out, which in turn caused the fan control module to stop working. The accessory fan has to draw air into the A/C compressor at idle in order to cool the car interior. If the accessory fan isn't working at idle, then the compressor won't get the required air and it won't cool the car's interior.
Also, check if the fans continue running at varying rpm for several minutes after you shut your car off. If so, the fan control module is likely at fault and will require replacement.