Im trying to recharge my system with a home kit, I see what I think is the high side right by the battery, I figured it was the high side because my connector wouldnt fit on it.

Is this where you put more refiridgerant in at?

99 F150 5.4l

 

yes

 

On my '99 Expedition, the High pressure side is in the front near the battery and the low (suction) side is down below the solenoid and wiring bracket on the filter/dryer. I wouldn't put freon in the high pressure side, especially if the unit is running. You can have pressures anywhere from 200 to 250 psi there which would blow the bottom of the can out. I was instructed that you should always add freon to the suction side. Spend a little money and invest in some gauges from Harbor Freight when they go on sale.