Ac high low port

Little hose high pressure big hose low pressure if this 134 (freon) charge hose will only fit one side Low pressure is charge side if really low may need a pro if you keep adding freon sooner or later the system will be Full no bubbles then you WILL need a pro. kittypower

 

Yup, like Kitty said.Fill from the top one.

 

Big line is low pressure port.

 

System has to be running.some times you may need to jump the low pressure switch as this shuts down compressor to prevent burnout.
You wont get accurate reading if compressor is not running.

 

Read the directions on the can. I believe they all say have the ac unit on and the setting at max cooling while you recharge / top off the unit. Also.....first time you need to do this it's fine to use a can of Freon that has "stop leak" type of additive. If you have to add more later get the straight / plain frepn. Too much of the stop lead type is not good. If you have to keep recharging the system then find the leak. That's all I got.