For M54 engine For A/C disconnection connect an approved refrigerant recovery/recycling/recharging unit to the A/C system and discharge it then raise the car and support it safely. Pop the splash shield out from under the engine, indicate the direction of rotation on the A/C drive belt and take it off. Following this, if equipped, then you have to be rid of the windshield washer reservoir and also the A/C pressure hose and suction hose flange bolts at the compressor, that you ought to plug instantly. When you are performing operations above the right front of the engine compartment, additionally, the hose of secondary air is to be fixed to get access to the A/C compressor. To demount the compressor, first remove the electrical harness connector from the compressor, then unsupport the compressor and remove the mounting bolts: on some models three bolts are used, on the others - four bolts. Removal is the opposite of installation where care is again taken to replace sealing O-rings when reconnecting refrigerant lines. If fitting a new compressor or if the compressor has been removed from the car for more than 24 hours then change the receiver drier core. Replace the A/C drive belt and align it to where the earlier made direction mark was, and recharge the A/C system as recommended by the equipment manufacturer. To start a new compressor, turn the A/C system 'ON', with the air vents open, turn the engine on, and allow it to idle, set the blower output to 75% and run the A/C for at least two minutes at idle speed ( ENG speed below 1500 rpm) Note: do not operate the new compressor at a high speed during start up to avoid damage. The N52 engined-clamp pressure of the A/C compressor is put in by nine aluminum fasteners which should be replaced; carry more as spares before removal and installation. As for the M54 engine: connect the refrigerant recovery unit; raise the car; remove the splash shield and A/C drive belt. Thus, rip out the coolant thermostat, as well as the A/C pressure hose and suction hose flange bolts from the compressor, and seal the hoses off. Once one has access to the A/C compressor, one has to unplug the electrical harness connector and then remove the compressor. The installation process is similar to that mentioned above, that is, the replacement of aluminum fasteners and the O-rings as well as the receiver-drier unit if it is applicable. Last, the A/C drive belt must be fitted and torqued as well as the system must be recharged, and do not rev the engine above idle to start with no matter how good the new compressor is.