Compressor HVAC: Description and Operation

A/C Compressor

- Only start engine after refrigerant circuit has been assembled.

- After installing a new A/C compressor or fresh refrigerant oil has been filled into compressor (e.g. after blowing through the A/C system), turn ribbed belt pulley of A/C compressor 10 rotations by hand before starting the engine. This prevents damage to the A/C compressor.

- If possible start engine only with a filled refrigerant circuit.

• The A/C compressor is always driven by the ribbed belt pulley (no A/C clutch):

• If an A/C compressor locks-up the overload protection for the A/C compressor shaft is triggered. An indication that the A/C compressor has locked-up is deformations/bumps on the ribbed belt pulley, but these are not always easy to detect. Another indicator is abraded rubber material in the area of the ribbed belt pulley.

• The A/C compressor is equipped with a protected oil supply, this prevents A/C compressor damage in the event that the system is empty. This means that approximately 40 to 50 cm3 of refrigerant oil remains in the A/C compressor.

• The engine may only be started when the refrigerant circuit is installed correctly. For example; if the refrigerant lines are not connected to A/C compressor, when the engine is running the A/C compressor may heat up (via internal heat generation) so much that the A/C compressor will be damaged.

• A/C Compressor Regulator Valve (N280) is not activated when the refrigerant circuit is empty and the A/C compressor idles with the engine.

• If it is necessary to start the engine with a discharged refrigerant circuit:

• Refrigerant circuit must be fully assembled.

• At least 1/4 of the prescribed refrigerant oil must be in the A/C compressor.

• No not rev engine higher than 2000 rpm.

• The engine should only run as long as absolutely necessary.

Note the following when starting engine for first time after filling refrigerant circuit:

- Start engine with A/C compressor switched off ("ECON" mode) and wait until the idling speed stabilizes.

- Open an instrument cluster vent.

- Select temperature preset "Lo" on A/C Control Head (E87).

- Now switch A/C compressor on ("Auto" mode) and allow engine to run for 5 minutes at idling speed.