BMW E34 air conditioning not cooling: refrigerant and compressor
Why does the E34 air conditioning not cool or the compressor not engage?
The most common cause is too little refrigerant: the A/C buttons light up only when there is pressure in the system. The leak can be, for example, in the condenser core. UV dye reveals it, because a suction-side leak test alone does not always find a leak.
How much refrigerant goes into the E34 air conditioning?
The fill amount for the R12 system is 1925 g ± 25 g. There are different figures for R134a, about 1550 g or 1925 g, so make sure you have the correct amount. Cars leaving the factory changed from R12 to R134a around 1992.
How is the air conditioning filled correctly after the system has been open?
The old refrigerant is removed and the system is evacuated for 30-45 minutes to remove moisture. The drier is always replaced just before evacuation. Every pipe joint has an O-ring, and an O-ring made for air conditioning is mandatory. The compressor outlet needs parts 64508390602 and 64508390603.
Is it normal for a clunk to be heard and the revs to rise when the air conditioning is switched on?
Yes. The clunk is heard when the compressor engages, and the idle speed rises on purpose. Selecting air recirculation also switches the compressor on without a separate A/C request, because the system dries the air.