Where is the ac low side service port located in the 2001 ford f150?

The 2001 Ford F-150 air conditioning low side service port is located on the passenger side of the engine compartment near the firewall on the side of the tank. There are two ports, the low side is the larger of the two. If recharging the AC system, the charging connector will only fit the low side port so mixing them up would be impossible. A trained technician can use the high pressure port, but only with the system off and using a vacuum pump to remove all the pressure in the system. The low pressure side is where the refrigerant is converted back to a liquid on its way back to the compressor to be changed back into a gas.