Why is my AC not cold when idling?

Cold at highway speed, warm at idle or in traffic is a textbook condenser-cooling problem. The AC condenser sits in front of the radiator and has to dump the heat pulled out of your cabin — at speed the wind does that job; at idle the electric radiator/condenser fan has to. Look for a fan that isn't spinning when the AC is on, a blown fan relay, a cracked fan motor, or bugs and cottonwood plugging the condenser fins. Systems slightly low on refrigerant also fail idle-first because head pressure climbs faster than the fan can shed it.

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