Refrigerant Circuit, Servicing
Refrigerant Circuit, Servicing
Working on the Refrigerant Circuit
Work on refrigerant system should only be performed in a ventilated rooms (workshops). Ensure that with in 5 meters circumference are no working-pits, basement staircases or shafts. Turn on the existing ventilation systems.
Reason
The refrigerant emerging is not only colorless and odorless, but also heavier than air and thus displaces oxygen. If refrigerant gas does escape even though all the safety precautions have been followed, there is a risk of suffocating in poorly ventilated areas and in workshop pits - even if it is not noticeable.
• The escaping refrigerant/air mixture should not be inhaled, but should be extracted via an existing exhaust-extraction ventilation system.
Do not attempt repair on filled air conditioning systems by soldering, brazing or welding. This pertains also for welding and soldering work on the vehicle, in the event that parts of the climate control system may heat up
Reason
Exposure to heat creates considerable pressure in the system, which could cause it to burst.
Corrective action
Discharge refrigerant circuit. Refer to => [ Refrigerant Circuit Draining ] Refrigerant Circuit Draining.
• Parts on the A/C that are damaged or leaking cannot be welded or soldered. They must be replaced.
When servicing air conditioner, all open components and pipe connections are to be immediately re-sealed.
Reason
Moisture will enter into air conditioner components if they are left open for a lengthy period. If this is the case, air conditioners cannot be refilled without having to replace parts of the system.
Without a high voltage system
• The A/C compressor without an A/C clutch (N25) is always also driven when the engine is running. If the vehicle has an A/C compressor without an A/C clutch , then the vehicle may only be started when the refrigerant circuit has been properly assembled. 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. Such internal heat generation results from the fact that - even with delivery near 0% - the compressor is operating with a fixed resistance (sealed circuit).
• An A/C compressor with an A/C clutch is installed as a running change on certain 4 cylinder vehicles from MY 12. Refer to => [ Belt Pulley with A/C Clutch (N25) Overview ] Belt Pulley With A/C Clutch (N25) Overview. The A/C clutch turns off the A/C compressor drive completely under certain conditions (for example "ECON"). The correct Climatronic control module must be installed and it must be coded correctly so that the Climatronic control module display and control unit can control the A/C clutch. Refer to the Electronic Parts Catalog, and to the Vehicle Diagnostic Tester under "Guided Fault Finding.
• To stop the A/C compressor from being destroyed when the refrigerant circuit is empty, it is designed such that delivery is reduced to roughly 0% and lubrication is maintained by way of an internal oil circuit with the oil left in the A/C compressor.
All vehicles
• Refrigerant in refrigerant circuit is never to be topped up (drain, evacuate and refill circuit).
• The entire amount of refrigerant oil to be added to the refrigerant circuit is in the replacement compressor.
• Different refrigerant oils are required for A/C compressors made by Denso, Sanden and Zexel/Valeo.
• Coat the O-ring seals lightly with refrigerant oil prior to installation. Refer to => [ Refrigerant Circuit O-rings ] Refrigerant Circuit O-Rings.
• The specified diameters for O-rings and the tightening torque pertain also to the threaded connections of the refrigerant lines or refrigerant hoses between the separate components.
• Only install O-rings that have been approved to be used with refrigerant R134a. Refer to => [ Refrigerant Circuit O-rings ] Refrigerant Circuit O-Rings.
• Check cooling performance. Refer to => [ A/C Cooling Output, Checking ] A/C Cooling Output, Checking.
• Check pressures in refrigerant circuit.
• All refrigerant circuit servicing and test procedures not described in this repair manual.
• Operate the A/C system after filling the refrigerant circuit. Refer to => [ A/C System, Operating after Filling Refrigerant Circuit ] A/C System, Operating after Filling Refrigerant Circuit.
• From the start of production through the change-over from MY 12, evaporators approximately 40 mm wide (block depth) are being installed (air conditioner part number "8K_ 820 005"). From MY 12, as a running change and depending on the version of the vehicle, an approximately 50 mm wide evaporator (block depth) is being installed (air conditioner part number "8T_ 820 005"). Pay attention to the correct allocation of the evaporator expansion valve (there are different versions). Refer to the Parts Catalog.
• Refer to => [ Refrigerant Circuit Component Overview ] Refrigerant Circuit Component Overview.