2001 F150 4 wd Crew Cab. With AC on low or medium, after a while, smoke comes out of the vents. I thought heater core leak and it was coolant misting. No, theres no oil film on anything. It looks more like fog. I disconnected the heater core to eliminate the possibility, and it still does it. Could it be freezing up? Compressor bad? It works great on high. Cabin gets cold so I turn it down, and then about 20 min later I get the smoke.

 

It's not smoke, it's fog. Enjoy the uber cold air while it lasts. Possible the low pressure switch isn't working properly but so long as you're not losing any air flow let it ride. If you notice low air flow output from the vents then it's time to diag.
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