Audi A4 Owners & Service Manuals

Audi A4: A/C System and Refrigerant R134a Safety Precautions

Vehicles with a high-voltage system (hybrid vehicles)

Extremely Dangerous Due to High-Voltage

The high-voltage system is under high-voltage. Electrocution can cause death or very serious personal injury from damages high-voltage components and high-voltage cables.

- Perform a visual inspection of the high-voltage components and the high-voltage cables.

- Never use tools that are for cutting, deformed, or sharp edged.

- Never use welding, soldering, thermal adhesive or hot air.

There is a Risk of Injury from the Engine Starting Unexpectedly

On electric - hybrid vehicles an active ready mode is difficult to identify. Parts of the body can be clamped or pulled.

- Turn off the ignition.

- Place the ignition key outside of the vehicle interior.

Risk of Damaging the High-Voltage Cables

Misuse can damage the insulation of high-voltage cables or high-voltage connectors.

- Never support objects on the high-voltage cables and the high-voltage connectors.

- Never support tools on the high-voltage cables and the high-voltage connectors.

- Never sharply bend or kink the high-voltage cables.

- When connecting pay attention to the coding of the high-voltage connectors.

For all procedures on vehicles with high-voltage system pay attention to the additional warning message for these vehicles. Refer to → Chapter "Warnings when Working on Vehicles with High Voltage System".

Vehicles with Start/Stop System

There is a Risk of Injury from the Engine Starting Unexpectedly

The engine can start unexpectedly on vehicles with an activated Start/Stop System. A message appears in the instrument cluster indicating whether the Start/Stop System is activated.

- Deactivate the Start/Stop System: Turn off the ignition.

All Vehicles


Asphyxiation, frostbite, and poisoning may occur as a result of leaking refrigerant

There is a risk of injury from leaking refrigerant

  • Danger of asphyxiation from displacement of the surrounding air
  • There is a risk of frostbite (or risk of freezer burn from the evaporating liquid refrigerant)
  • There is a risk of poisoning from the byproducts

Corrective Action

  • Work on the A/C system refrigerant circuit should only be performed in well ventilated areas.
  • When handling refrigerant and working on the refrigerant circuit, make sure there is a good flow of oxygen (change the air at least one time each hour in the work area and three times per hour in enclosed spaces (for example, the work pit). Turn on the available workshop ventilation and exhaust systems.
  • Only store containers and devices with refrigerant in well ventilated areas (not in basements or near basement staircases for example).
  • Do not breathe in fumes from leaking refrigerant.
  • When handling refrigerant and when working on the refrigerant circuit, wear suitable protective gloves and protective eyewear.
  • It is recommended to have an eye-flushing bottle available.
  • Work on the A/C system refrigerant circuit should only be performed in well ventilated areas. Switch on the available ventilation systems.
  • Refrigerant must not be stored in low-lying areas such as basements or in their entry ways or windowsills.

First Aid Measures

  • If the affected person has inhaled a high concentration of refrigerant vapors, immediately remove them from the contaminated area and bring and lay them in the fresh air. Keep the affected person warm and calm. Initiate artificial respiration if the affected person is experiencing troubled breathing and administer oxygen if necessary. If the affected person has difficulty breathing or cannot breathe, tip head back and perform mouth to mouth respiration. Consult a physician.
  • Should liquid refrigerant come into contact with the eyes, rinse eyes thoroughly in water for approximately 15 minutes. Then apply eye drops and consult a doctor immediately, even if the eyes are not hurting.
  • Never put anything in the mouth of an unconscious person. If the symptoms continue or if ever there is a concern, seek medical advice.
  • 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 or lukewarm water.
  • If contact with eyes or mucous membranes occurs, immediately rinse with copious amounts of running water and consult an eye specialist.
  • Immediately remove clothing that refrigerant has contacted and rinse the area of the skin affected with cold or lukewarm water. Do not use hot water. Seek medical attention if frostbite occurs.


  • The refrigerant has a faintly noticeable odor which is therefore not perceptible.
  • The refrigerant is heavier than air and falls to lower lying areas such as the work pit, basements, and deep spots and displaces the breathable air and oxygen. Remaining in oxygen deprived areas is life endangering.
  • Liquid refrigerant for example from a leak evaporates at an ambient pressure of approximately 1 bar at roughly -29 ºC (84 ºF). If the refrigerant evaporates on skin, it can cause cryogenic burning. Delicate organs for example the cornea, are especially at risk. Excessive frostbite may be life threatening.
  • The refrigerant breaks down near flames or when it comes in contact with hot surfaces. There is a danger of becoming poisoned by the resulting toxic fumes if inhaled. A pungent odor indicates that the products of the 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.
  • The specific dangers associated with the refrigerant, material data etc. can be found in the safety data sheets.

Never weld or hard/soft solder components of a filled A/C system. This also applies to welding and soldering on the vehicle, if there is a risk that it may heat up components in the A/C system. When performing paintwork repairs, the temperature in the drying booth or preheating zone must not exceed 80 ºC (176 ºF).


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

Corrective Measure:

- Discharge refrigerant circuit using A/C service station.


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

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

Corrective Measure:

- Reservoirs must never be completely filled with liquid refrigerant. Without sufficient room for expansion (gas cushion), reservoirs will rupture with devastating effects in the event of a temperature increase. Refer to → Chapter "Refrigerant R134a Characteristics".

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

Corrective Measure:

- Evacuate systems and reservoirs before charging with refrigerant.


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