You don’t. You’ll shoot your eye out by freezing it if you don’t know what your doing.

First of all, you need some dye to find out why you are re-charging your A/C.
& if you do do-it-yourself, then watch that low-pressure cycling switch. They blow easily when you don’t know what you are doing?

ok,first of all,if it needs recharging then there IS a leak.This has to be repaired or its just going to leak out again.So now you need a leak detector which is more expensive then getting someone to repair it.Can you see where this is going? I wont go into it but it gets better($$$$$$).Bite the bullet and take it to a tech that has the proper equiptment to do the job right the first time.

other than the fact that you can kill yourself or cause serious injury…. please don’t attempt. I know you’re trying to save money, but the risks are too high and costly

Ok,You CAN do it yourself.Go to the parts house,or even Wal-Mart,in the automotive section,and buy an r-12 to 134-a recharge kit.It will have the coolant with it,and will give you instructions.However,they do not recommend using that in a unit that has not been professionally switched over,but I have always done my own.Make ABSOLUTELY sure that you put the coolant in the proper port.You can tell which one,as the wrong port gets a LOT hotter than the proper one.It is easy and cheap to do,if you follow the instructions.It comes with a gauge that will show you when it gets properly filled.

Don’t even think about it.

Take it to a professional and get it done properly

These guys cost because they are experts, have the licences and the equipment.

Let them do what they are trained to do.

P.S I am not an air-con engineer, I pay to have mine done

Hope this helps

first you have to have the tools to do if with ,and no you have to change it to the new kind they useing,,be cheaper to let a shop do it,,check around for the best pris

I may be totaly wrong but I dont think (unless you are a licensed heating and air professional) you can even buy the refridgerant commercialy anymore. You may want to get more oppinions or check with your local Auto Zone or automobile parts supply store.