Basic Rules

Basic Rules For Working On Refrigerant Circuit

- Observe workplace-specific instructions refer to Environmental Protection Vol. 2-2.23.0.
- Ensure absolute cleanliness when working.
- Wear safety goggles and gloves when working with refrigerant and nitrogen.
- Switch on existing ventilation systems.
- Use service station to discharge refrigerant circuit, only then open screw connections and replace malfunctioning components.
- Use caps to seal off opened assemblies and hoses to prevent ingress of moisture and dirt.
- Make exclusive use of tools and materials intended for refrigerant R134a.
- Re-seal opened refrigerant oil vessels to guard against moisture.
- Flush refrigerant circuit with compressed air and nitrogen if:
- Moisture or dirt has penetrated into refrigerant circuit (e.g. following an accident)
- Refrigerant oil is dark and viscous.
- There is too much refrigerant oil in the refrigerant circuit after compressor replacement.
- The A/C compressor had to be replaced on account of "internal" damage (e.g. noise or no output).

In vehicles with A/C compressor without A/C clutch:

NOTE:
- The engine is only to be started following complete assembly of the refrigerant circuit.
- If possible start engine only with a filled refrigerant circuit.
- A/C compressor is driven permanently by the ribbed belt pulley/torsion elastic clutch (not installed with an A/C clutch):
- If an A/C compressor locks-up the overload safeguard for the A/C compressor shaft is triggered. Also if no outward bulges are visible on ribbed belt pulley/ overload safeguard, it may also be that the A/C compressor is locked up. Another indicator is abraded rubber material in the area of the ribbed belt pulley/overload safeguard
- 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 approx. 40 to 50 cu.cm of refrigerant oil remains in the A/C compressor.
- The engine should only be started when the refrigerant circuit is completely and properly installed. For example; if the refrigerant lines are not connected to the A/C compressor, when the engine is running the A/C compressor may heat up (via internal heat generation) so much that the compressor will be destroyed.
- 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.
- Engine speed should not increase above 2500 RPM.
- The engine should only run as long as absolutely necessary

O-ring seals
- Make exclusive use of seals which are resistant to refrigerant R134a and the related refrigerant oils. Color coding of O-rings is no longer employed. Colored and black O-rings are used.
- For used O-rings, make sure inner diameter is correct.

Parts Catalog
- Use O-rings only once.
- Before installing O-rings, coat lightly with refrigerant oil (PAG oil).

NOTE:
- When flushing components with compressed air and nitrogen, always extract the gas mixture escaping from the components using suitable extraction units (workshop extraction system).
- After ending all service work, screw sealing caps (with seals) onto all connections with valve and service connections.

Before starting up A/C system. Observe vehicle specific filling capacities.

Do not top off refrigerant, extract refrigerant present and fill the system anew.

Before starting up A/C system after fresh charging
- After installing a new A/C compressor or fresh refrigerant oil has been filled into compressor (e.g. after flushing 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
- For5-cyl. and 10 cyl. diesel engines, rotate A/C compressor 10 rotations by hand at overload safeguard. After that, install A/C compressor. This prevents damage to the A/C compressor
- Start engine with A/C system (A/C Clutch N25 and A/C Compressor Regulator Valve N280) switched off.
- Following engine idling speed stabilization, switch on A/C compressor and run it for at least 10 minutes at idling speed with maximum cooling output.