We call it refrigerant. Text books on ac system refer to it as refrigerant Not freon.

Its a teachable moment. A lot of people still call all refrigerants Freon and that's OK with me, just as long as they don't go around calling every plain old table tennis game "ping-pong". That one really chaps my a---.

On my 2001 4.4i - the red cap is the high pressure side. But, you can't always go by the cap color as it is not standardized. I've been tinkering on a Mini Cooper S this week and both caps are black.

On the E53 4.4i, the low pressure valve is in the line between the engine block and the passenger strut tower. The high pressure valve is close to the radiator.

The good news is that they are not interchangeable sizes - For a 134A system, the high pressure quick connect is the larger one. The low pressure quick connect is the smaller one. You fill from the low pressure one.

The catch is that BMW made it hard to fill correctly - some systems can be filled by pressure and so a cheap fill kit with a pressure gauge will get you close enough if you know the pressure to look for (which depends on the outside temperature and humidity). For these cars, BMW specifies a fill by weight, but there is no way to know what is currently in the system unless you pump whatever is in there out (recover it, don't vent it) and then fill it to the correct weight. In theory, you can get a shop to do the recovery for you, and fill it yourself, but good luck finding one that will.

Its been a few years since I took my EPA test (I did), but I believe it remains legal to top off a system leaking up to 15% a year. May not be the greenest thing, but there is no requirement (and no such thing) as perfectly sealed system if you have rubber hoses and rubber o-rings (which they all do). The refrigerant will diffuse through the rubber at some slow rate, even when everything is working as designed.

The original post says "I've got the right side wont cool thing"..... Do the other vents throw cold air? If they do it is not a refrigerant issue, it's a issue with the stepper motor or the temp control. Do the other vents have cold air coming out ? If so it has nothing to do with the amount of freon in the system. The term "freon" is like the term "kleenex". A popular brand name synonymous with refrigerant. I am a A/C service tech for 35 yrs.

My experience with my (purchased new) 04 4.4i and that of others here contradicts your statement.

I have recharged the AC system 3 times in the vehicle's lifetime, with my mechanic, using around 1 can of R134A each time. Each time, the symptom was that the right side vents were not cooling properly. Each time, it turned out that the system was low on refrigerant and the problem went away for a few years.

One thing my mechanic recommends is having someone in the vehicle revving the engine to approximate 3k while recharging the system. He is a master BMW mechanic (though retired from the dealership) so l follow his advice.

I've never heard of that. I don't see how it is possible. There is one evaporator coil that supply's cold air to all the vents. The air temp out of the vents is controlled by mixing air from the evaporator and the heater core air. I'ts whats called "hot deck / cold deck" system. If the other vents blows good cold air, thats air straight out off the evap coil. The right side should blow cold too. Unless the control or sensor or stepper motor is mixing in warm air from the heater core or "hot deck". I doubt its a refrigerant charge issue.

Do a little searching here and you will see that it is common on E53s. Three times my system has been fixed by adding R134a and each time the right side ventilation was warm and the left side still cool. I don't understand the physics of it but the gauges showed that the refrigerant was low and adding it fixed the problem.

@hvacdude - just had the right side blowing warm air issue 2 weeks ago. Added some r134a, and now ice cold from both sides.

Doesn't make sense to me, but apparently so, from what a lot of you guys are saying. :dunno:

Add me to the list that has the right side with warm and the left with cool. Added some 134a and it was fixed. This was a few years ago that I did it. No problems since.

What special equipment if any did you have to have with it?