Volkswagen Tiguan Service and Repair Manual: A/C System Operation, Safety Precautions

A/C System Operation

The temperature in the passenger compartment depends on the amount of heat radiated through the windows and conducted by the metal parts of the body. In hot weather it is possible to achieve a more comfortable temperature for the passengers by pumping off some of the heat.

As heat spreads into cooler areas, the passenger compartment is equipped with a unit for generating low temperatures. In the unit, refrigerant is constantly evaporated. The heat required for this is extracted from the air flowing through the evaporator.

After absorbing heat, the refrigerant is pumped off through the compressor. The action of the A/C compressor increases the heat content and temperature of the refrigerant. Its temperature is then substantially higher than that of the surrounding air.

The warm refrigerant flows to the condenser. There, the refrigerant dissipates its heat through the condenser to the surrounding air due to the temperature difference between the refrigerant and air.

The refrigerant thus acts as a heat transfer medium. As it is to be reused, the refrigerant is returned to the evaporator.

For this reason all air conditioning systems are based on the refrigerant circulation principle. There are however differences in the combination of aggregates.

Safety Precautions

General Safety Precautions

• As per VBG 20, German industrial liability insurance association.
• Follow the instructions for the workplace. They should be displayed in the workplace.

Product Characteristics

Refrigerants used in motor vehicle air conditioning systems belong to the new generation of refrigerants based on chlorine-free, partially fluorinated hydrocarbons (H-FKW, R134a).

With regard to their physical properties, these are refrigerants which have been liquefied under pressure. They are subject to the regulations governing pressure vessels and use is only to be made of approved and appropriately marked containers.

Compliance with specific conditions is required to ensure safe and proper use.

Handling Refrigerant

WARNING

There is a danger of ice-up.

The refrigerant can then escape as a fluid or vapor.

Do not open containers which store refrigerant.

If refrigerant vessels are opened, the contents may escape in liquid or vapor form. This process is intensified the higher the pressure in the vessel.

The pressure level is governed by two factors:

• The type of refrigerant in the vessel. "The lower the boiling point, the higher the pressure."
• The temperature level. "The higher the temperature, the higher the pressure."

Protective Eyewear

Put on protective goggles. They prevent refrigerant getting into the eyes, as this could cause severe injury from exposure to cold.

Protective Gloves and Clothing

Greases and oils dissolve readily in refrigerants. They would therefore destroy the protective layer of grease if allowed to come into contact with the skin. Degreased skin is however sensitive to the cold and germs.

Fluid Refrigerant and Skin Precaution

The refrigerant draws heat for evaporation from the surrounding area. Even if this is the skin. This may cause extremely low temperatures. Local frost bite may result (boiling point of R134a: -26.5 ºC (-15.7 ºF) at ambient pressure).

Do Not Breath In Refrigerant Vapor

Note

If highly concentrated refrigerant vapor escapes, it mixes with the surrounding air and displaces the oxygen necessary for breathing.

Welding and Soldering on Refrigeration Systems

Before performing welding or soldering work on vehicles near the air conditioning system components, extract the refrigerant and remove the residue by flushing with compressed air and nitrogen.

The products of refrigerant decomposition due to the effect of heat are not only toxic, but may also have a highly corrosive effect on pipes and system components. They mainly take the form of hydrogen fluoride.

Pungent Odor

A pungent odor indicates that the products of decomposition mentioned above have already formed. Avoid inhaling these substances under all circumstances, as otherwise the respiratory system, lungs and other organs could be damaged.

First Aid

• Following contact with eyes or mucous membranes, immediately rinse with copious amounts of running water and consult an eye specialist.
• Following contact with the skin, immediately remove affected clothing and rinse skin with copious amounts of water.
• Following inhalation of highly concentrated refrigerant vapors, immediately take the affected person into the open air. Call a doctor. Administer oxygen in the event of breathing difficulties. If the affected person has difficulty breathing or cannot breathe, tip head back and perform mouth to mouth respiration.

Handling Pressure Vessels

• Secure vessels to prevent them falling over!

Secure upright cylinders to stop them falling over and cylinders lying flat to stop them rolling away.

• Do not throw vessels!

If dropped, the vessels could be so severely deformed that they rupture. The refrigerant evaporates immediately, liberating considerable force. Flying fragments of cylinders can cause severe injuries.

Valves may break off if cylinders are not properly transported. To protect the valves, cylinders are only to be transported with protective cap screwed on.

• Never store in the vicinity of radiators.

High temperatures may occur next to radiators. High temperatures are also accompanied by high pressures and the maximum permissible vessel pressure may be exceeded.

Not Warming Above 50 ºC (122 ºF)

To avoid possible risk, pressure vessel regulations specify that vessels are not to be heated to in excess of 50 ºC (122 ºF).

Heating Warning

Do not heat with a naked flame under any circumstances. Localized overheating can cause structural changes in the vessel material, which then reduce its ability to withstand pressure. There is also a danger of refrigerant decomposition due to localized overheating.

Empty Containers

Empty refrigerant vessels must always be sealed to prevent the ingress of moisture. Moisture causes steel vessels to corrode. This weakens the vessel walls. In addition, rust particles entering into refrigeration systems from vessels will cause malfunctioning.

Extraction and Charging System Safety Regulations

• Make sure the shut-off valves are closed before connecting the charging system to the air conditioning system.
• Make sure the process is finished before disconnecting the charging system from the A/C system. This prevents any refrigerant from escaping into the atmosphere.
• Once the purified refrigerant from the charging system has been transferred to an external compressed-gas cylinder, close the hand shut-off valves at the cylinder and charging system.
• Do not expose charging system to moisture or use it in a wet environment.
• Disconnect from power supply before performing service work on the charging system.
• Never use an extension cable on account of the fire hazard. If the use of an extension cable is unavoidable, the minimum cross-section should be 2.5 mm².
• In case of fire, remove the external cylinder.
• Entrained oil from the air conditioning system drawn by the suction unit into the measurement vessel supplied is subsequently to be transferred to a sealed container as it contains a small quantity of refrigerant. It must not be released into the environment.
• Following shutdown, A/C service station is to be secured to stop it rolling away.

A/C System and Refrigerant R134a Safety Precautions

A/C Service Station -VAS6007A- (and further or current A/C Service Station)

Refer to the Workshop Equipment Catalog.

WARNING

• It is recommended to have an eye-flushing bottle available.
• If liquid refrigerant has come in contact with your skin and eyes, immediately flush with cool water for 15 minutes. Afterwards instill eye drops and consult a doctor immediately, even when the eyes are not hurting.
• The doctor must be informed that the injury was caused by refrigerant R134a. Should refrigerant come into contact with other parts of the body despite compliance with safety regulations, these must likewise be rinsed immediately for at least 15 minutes with cold water.
• Work on refrigerant system should only be performed in ventilated areas (workshops). Turn on the exhaust gas ventilation system
• Refrigerant must not be stored in low-lying areas such as cellars or in their entry ways or windowsills.
• Do not attempt repair on filled air conditioning systems by soldering, brazing or welding. This applies also for welding and soldering work on the vehicle, in the event that parts of the A/C system may heat up. When performing paintwork repairs, the temperature in the drying booth or preheating zone must not exceed 80 ºC (176 ºF).

Reason:

Exposure to heat increases the pressure in the system, which could cause the pressure relief valve to open.

Corrective measure:

• Discharge refrigerant circuit with A/C service station.

Note

Always replace damaged or leaking A/C system components. Do not attempt to repair them by soldering, brazing or welding.

Refrigerant containers (for example, charging cylinders of A/C service station) must never be subjected to excessive heat or exposed to direct sunlight.

Corrective measure:

• Vessels must never be completely filled with liquid refrigerant. Without sufficient room for expansion (gas cushion), vessels will rupture with devastating effect in the event of an increase in temperature.

Refrigerant is never to be transferred to systems or vessels in which air is present.

Corrective measure:

• Evacuate systems and vessels before charging with refrigerant.

Refrigerant Circuit, General Precautions

• Follow the instructions for the workplace. They should be displayed in the workplace.
• Ensure absolute cleanliness when working.
• Wear work clothing, safety goggles and gloves when working with refrigerant and nitrogen.
• Turn on the exhaust gas ventilation system
• 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.
• Be sure to close the container to prevent the refrigerant from absorbing moisture from the air.

 

• Refrigerant Circuit, Flushing with Compressed Air and Nitrogen.
• Flush the refrigerant circuit with R134a refrigerant.

On vehicles with A/C compressor without magnetic clutch:

Note

• The engine should only be started after assembling the refrigerant circuit.
• If possible start engine only with a filled refrigerant circuit.
• The A/C compressor is always driven by the ribbed belt pulley/torsion elastic clutch. It does not have a magnetic clutch.
• If an A/C compressor locks-up the overload protection for the A/C compressor shaft is triggered. If no bumps are visible on the ribbed belt pulley/overload protection, the A/C compressor may be blocked. Another indicator is abraded rubber material in the area of the ribbed belt pulley/overload protection.
• 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 pipes 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 a quarter of the prescribed refrigerant oil must be in the A/C compressor.
• Do not let the engine RPM go above 2,000.
• The engine should run less than 10 minutes.

O-ring

• Only O-rings that are resistant to refrigerant R134a and refrigerant oil must be installed. Color coding of O-rings is no longer employed. Colored and black O-rings are used.
• Ensure inner diameter on seals used is correct.
• O-rings may only be used once.
• Before installing, coat the O-rings lightly with refrigerant oil (PAG oil).

Note

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

Before starting up A/C system. Pay attention to the vehicle-specific filling capacities.

Do not fill refrigerant, extract the refrigerant present and refill the system.

After Charging A/C System

• 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.
• For 5-cylinder and 10-cylinder diesel engines, rotate A/C compressor 10 rotations by hand at overload protection. Then install A/C compressor. This prevents damage to the A/C compressor.
• Start the engine with the A/C turned off (A/C Clutch -N25- and A/C Compressor Regulator Valve -N280- are not actuated).
• 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.