Originally Posted by Crowz

A weak ac clutch will come and go during a day of use if it engages at all. So again if after running the car for a bit it cools fine for the rest of the day its the compressor.

The "tool" as you put it will show no pressure with the clutch engaged or not. So its not going to diagnose the variable compressor even if it had a bad clutch. Also all compressors sold today for the x5's comes with a new clutch.

A set of gauges are not going to diagnose this problem. The are nice to have when charging the system after changing to compressor but your not going to solve this one with gauges.

It cools or it doesn't when this is the problem. If its not cooling the gauges shows nothing and the air out the vent is hot.

If its cooling it shows pressure and the air out the vent is cold. Not any new data here via the gauges that you didn't have already just by feeling the air coming out the vents.

Any other problems then sure gauges are the way to go for the most part but when it comes to this unique problem on the x5's at least when it wont cool when first used for the day but works fine all day long till you let it sit just replacing the compressor is the correct solution always.

My e70 does the same thing but its in the early stages or by design. It doesn't cool for about a minute or longer when first cranked. It will get worse with time.

The symptoms for this problem start with 2 minutes then 5 then 10 and then 30 minutes.

Then its over an hour.

The e53 was taking as long a 2 hours right before I replaced the compressor finally.

I have been fixing a/c systems for about 30 years and have never run into this till the E53 did it and after researching it I found plenty of tech papers on it and others that had the same issue. I had never dealt with vehicles using the variable compressors before this.

As for gauges I have some rather nice ones but again they were useless for diagnosing this particular issue. I could see the high side and low side pressure. I could see the high side temperature and low side temperature with my gauges. They displayed everything I needed to know from type of Freon, amount needed for the charge, recommended high and low side pressure readings, ideal low and high side temperatures, etc. But again they were useless for fixing this particular problem.