mine is a 2003 cooper s, wonder what the freon pressure should be? As the air con seems has no cool air, i think the freon might leaking and wanna refill it, thanks

 

Not just a matter of adding refrigerant. If you add too much, you can make matters worse. The stuff just doesn't vanish if it's a sealed system. You will need to have a vacuum drawn on the system to determine if/where you have a leak. After that's determined/fixed, the system should be filled with the exact amount of refrigerant specified on the sticker in the engine compartment.

 

Should be r134A....NOT FREON....
just refilling with a random can CAN cause issues...
"refill"cans USUALLY has extra oils added.....often not the right type...and you have no idea how much is still in the cooling system....
adding a DIY refill can COST you more than it saves due to later repairs...
But a tip...
THE ENTIRE MINI AC system IS TINY!!
Hold about a POUND from empty!! So when/IF yo buy a kit to diy it...only a small amount is used...often a FRACTION of the can made for larger cars/SUV's....
Know that you may "fix"the issue for a few weeks or months...but may need to have a pro replace the compressor, etc for $1000+ just cause the system was overfilled or had the wrong oil added that was too thick/thin for the compressor...or not enough...or more common...folks say...MY AC sucks after refilling...common issue...caused by too much oil....the system has a fixed volume...too much oil results in less volume for the r134a to expand and contract.....
Safest thing...have a shop service it.....they have the tools, skills, and knowledge...
But if it is a "hoopty" and you just want to try to make it work...add a small amount from a kit...pay attention to the gauges on the kit....one warning...
all the kits REQUIRE the compressor be running...if it is off...they cannot work...and if the PSI gets too low...a pressure switch in the system shuts of the compressor....kind of a catch 22....

 

Scary question, judging by the way it was worded OP your best bet is to look around for a mechanic to have a look at it. Don't worry too much about it being a Mini, it is a fairly common BMW system used on many brands of cars; just look for honest A/C specialists in your area because they have seen everything. Maybe you have heard rumors that you can just "top off" a sealed A/C system, and while some of those are probably true in some specific situations with some larger capacity (and much OLDER systems), there are a lot more horror stories of a modern system being totally whacked by the amateur. Pinch pennies elsewhere, let the experts in on this one and you will not regret it if you can find an honest one.

Anyway, my ex-wife tree hugger <banned word> sez you are just destroying mother earth by not fixing the problem of why the old refrigerant leaked on a sealed system. The penguins in Antarctica need your support, stop increasing the ozone layer hole over their home!

 

Good advice above; avoid those a/c refill cans.

 

This, R135a systems will blow hot at the slightest overcharge.

 

I too recommend going to a shop and letting them check your system; I can get a complete system check and service for $25 plus cost of refrigerant IF NEEDED.

But to answer your question the 'pressure cap opening pressure' should be 0.89 to 1.2 bars according to Haynes. total quantity is 415g +/- 10g of type R134A

 

Thanks for advises, will bring it to shop to have a look, luckily weather still cool here