Yes leave it closed. There is no need to open or remove the High (red) cap.

 

Ok i started doing it, and yes my pressure was low. but i stopped becuase i didnt know how to read the gauge while its going on. does the needle go up on its own while its filling or do you have to turn it off then read the gauge again?

 

Here are step by step instructions
1. Start the car
2. Put the A/C on high
3. Shake up the can
4. Connect the can to the low pressure side
5. Read the gauge
6. If it shows low pull the trigger let some in then read the gauge again
7. Keep doing this until the gauge shows at the top of the green zone

 

Thanks you everyone for your help. I just got done and my a/c now is icey cold.

 

it's about time for me to do this as well.

 

After how long is it a good idea to check the level in the AC ?

 

you'll feel it start blowing warm/not cold air

 

i'm gonna do mine tomorrow before i go to vegas. what stuff did you end up getting?

 

I have lancer 2007 and i need to know if any one can help me where can i find the charging details for the ac i need to know how much weight I'll charge

 

this? it's all I could find in 5 minutes...