Hi, I do not see that your question has been answered, so I will answer it since I also have a 2004 superduty.
You add a/c gas to the low pressure port between the passenger side battery and the radiator. It has a black cap, and your a/c equipment should have the right fitting to attach to this no problem. Good luck!
R134a
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Which do i hook to to charge the freon in a 2004 ford expedition
I had an additive put in my Lincoln ls. I bought the adapter needed to add freon. It was located on driver side in front of tire.
on the low side pessure port of the compressor line
Freon is added in the low pressure port of the ac system. It is on an aluminum pipe on the passengers side, close to the ac drier.
Buy a kit at Wal-mART OR AUTO PARTS COMES WITH INSTRUCTIONS
You don't add Freon as it has R134a not Freon. You add it to the low pressure side which is the larger hose.
Take it to the a auot shop. you can not add freon
Contains no Freon. Freon was banned beginning in 1996.
where do I add freon to my air conditioning unit on a 1997 chevy truck?