So I'm approaching 100,000 miles ('04 e60) and in this hot weather, I see the A/C is pooling a lot weaker, so I went to local auto parts store and picked up a can of refrigerant booster. It says to unscrew the A/C charge intake, or whatever you call it, looks like a pimple with a cap screw, and to add the contents.

My question is, which cap? I see two of them. One is right on the edge, left side front, under the hood. The other one is back, toward left middle of the engine, with silver HVAC running around it. Do I add refrigerant to one, both, which one?

Thanx.

If you try and pick the high pressure side by mistake it could be a bad situation. You should find a trained tech for A/C work.

The refrigerant can will only fit one connector, the small size one. Have had very bad experiences with top up - the last one ended with the AC compressor stalling on the drive belt. There is no substitute for a proper AC evacuate and refill by a competent person with the proper equipment to ensure contents are removed and the right amount is returned. The refill should include lubricant and hopefully a fluorescent dye to trace leaks.

Also check to see if the microfilters have been changed regularly.

did you get the can with a gauge on it? you should.
the tip only goes on the low pressure side port.
plug it in while the ac compressor is on, and add as needed until the gauge shows the proper range.

You should buy the refriderant can with the gauge included. It should include synthetic lubricant and sealer. Example:


Start your car put your A/C on high load. If you choose MAX A/C on the E60, make sure to have your top air vent on with one indicator bar in your idrive. Let it get to maximum cooling capability. If it is not cooling, listen for the clutch engagement. It should kick on then off. If not, you have another issue.

The can's gauge will only fit on the corresponding connector on your vehicle.
Once you connect the gauge then you will see the gauge needle go up.
Now, this is very important........when the A/C clutch is engaged is when you read the indicator. Your gauge may have colors. However when engaged you should be at about 35 max. Never fill it all the way up because you will hinder the A/C's ability to cool rapidly. When the clutch disengages, or you shut off the A/C, you will go into the warning area of the gauge. Don't worry about this. As long as you're in the blue and at about 32-35 you're good to go. Hope that helps.

P.S. make sure you shake that can first.

For those who may be interested see forums.5series.net/uploads/1155867731/gallery_237_213_2073842.pdf which will tell all there is to know about E60/61 AC systems. For instance there ain't no clutch so there is no good listening for it clicking in.

If the link don't work, here is the pdf

thats interesting. so there is an electric control valve on the compressor itself which bypasses or pressurizes the ac system.

That's what I thought at first. The article takes some reading (page 4 AC Compressor [more...]) - the control valve influences the swash plate angle and hence the stroke on the 7 pistons in the compressor. It appears that the compressor is never idle when the engine is running and can work between 2% to 100%, the minimum to maintain lubrication. Also if the compressor stalls (blocks), there is a rubber connection between the drive pulley and the input shaft that not only absorbs vibrations but allows slip to avoid damage.