A/C issues

[Richard991]

E70 4.8 V8. Now the weather is warming up it is obvious that the A/C is not functioning.
I checked it a month ago and it was low in gas but not empty so it was topped and appeared to work - for a while. I need to put the gauges back on but I am puzzled as the compressor nose is turning even if the A/C button is off. Obviously needs more investigation but if the compressor is engaged and there is gas I should be seeing a cooling effect.
Does anybody have the parts list and are the compressors different over the different engine types?
Richard

[X5Sport]

The compressor pulley runs all of the time and uses an electronic clutch to engage when cooling is required.

Realoem is the place to search for parts - it’s a copy of the OEM Parts database. Use the last 7 of your VIN to pull up your model. You can use part numbers on there to find equivalents cheaper on line.

Newtis.info has a copy of the Service instructions.

If it isn’t cooling then low gas is the usual cause. The compressor won’t ‘engage’ if the pressure is too low. Probably worth getting a leak test done if it’s lost gas again. One of the issues with modern a/c systems is that the seals dry out unless the system is used regularly. I never turn mine off as it makes no real difference to fuel consumption (unlike those of 30 years ago). When re-gassing, it is essential to have a lubricant added at the same time to keep the seals good.

[Richard991]

Like the Porsche 928 systems I work on the noseplate in front of the pulley should not rotate if the system is off or there is low gas, I believe?
Mine rotates all the time and if I grip it to rotate it by hand (engine off of course!) it feels solid. I think it has become welded to the pulley and is rotating despite there not being enough (any) gas. It is probably the compressor itself which is buggered and now leaking.
The link is useful. Thanks
Richard

[Alan Gunn]

As above it should spin all the time.
You should here a click when the AC button is pressed get someone to sit in and press the button while you listen under the bonnet.

[Richard991]

Just to be absolutely clear, the plate that sits in front of the compressor pulley (sort of 3 legged shape) rotates with the pulley ALL the time and the mag clutch is inside. You see no difference from the outside when the clutch engages/disengages?
Different from any other compressor I have seen where the very front part is attached to the compressor drive and only rotates when the clutch is engaged.
Richard