Leak detection with forming gas

Certain user behaviors can lead to a loss of refrigerant from the refrigerant circuit even if there is no leak. This may occur if the customer has not used the air conditioning for a period of more than six months. This may cause O-rings to harden and refrigerant may leakage. In this case, it will be sufficient to fill the refrigerant circuit again and switch on the air conditioning for approximately 10 minutes while the engine is running.

Preliminary work needed: 

• If components of the refrigerant circuit are contaminated, clean the engine compartment. Otherwise, the sensor head of the leak detector will become contaminated. 

  Comply with NOTES AND INSTRUCTIONS on handling high pressure cleaner.

• Drain off air conditioning system. Refer to: SUCTION, EVACUATING AND FILLING AIR CONDITIONING (R134A)  or SUCTION, EVACUATING AND FILLING HEATING AND AIR CONDITIONING SYSTEM (R134A)  or SUCTIONING, EVACUATING AND FILLING HEATING AND AIR CONDITIONING SYSTEM (R1234YF) .
• Fill the air conditioning with forming gas
• Set pressure to 5 bar

To reach the components of the refrigerant circuit with leak detector, specific parts must be removed depending on the vehicle.

Remove the following parts first immediately before the check of the respective components: 

• Drive belt from air conditioning compressor
• Center fresh air grille
• Covers
• Trim panels
• Air ducts
• Intake silencer
• Bulkheads
• Parts of the interior equipment (automatic rear air-conditioning system)

In some vehicles it is necessary to open the air flaps of the automatic air flap control.

Vehicle-specific notes: 

Only I01: 

To access the connections for the refrigerant lines, remove front luggage compartment well.

Only I12: 

Only BMW i and hybrid vehicles: 

Carry out the following test module to guarantee practically complete draining of the refrigerant circuit or hybrid battery cooling system: 

• Body
• Air conditioning function
• Drain/fill the refrigerant circuit
• Drain/fill the refrigerant circuit
• Drain/fill the refrigerant circuit of the heat pump (only I01 with heat pump)

Delete fault memory after filling the refrigerant circuit.

This is absolutely necessary to find certain leaks, such as in the area of the O-rings.

If no leak is detected, repeat the leak detection with 10 bar  .

Forming gas consists of 95% nitrogen and 5% hydrogen. The leak detector will detect hydrogen. If this is leaking from the refrigerant circuit even though the pressure remains, the leak detection bears no results.

Maximum approved pressure: 10 bar 

Do not start  the engine during the entire procedure!

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Notes for handling the leak detector: 

1. Sensor head should always stand vertical to the surface to be checked.
2. Sensor head must always be aligned to the center of the point to be checked. Slowly guide the sensor head around the point (e.g. connection point, sealing surface, etc.).
3. The optimal distance (A) between sensor head and surface to be checked should permanently be approximately 1 mm.

   Maximum distance (B) at points that are difficult to access approximately 5 mm.

4. Checking speed may not be more than maximum 2 cm per s.

Then check if the leak is still displayed at the same point. Repeat the process up to three times,

to ensure that a leak is actually present at this point.

Non-compliance will significantly reduce the efficiency of leak detection!

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Overview of positions to be checked: 

1. Air conditioning condenser
2. Connection point between air conditioning condenser and refrigerant line
3. 1. Expansion valve, front (vehicles with and without automatic rear air-conditioning system)
   2. Expansion valve, rear (vehicles with automatic rear air-conditioning system)
4. Air conditioning compressor
5. Filler neck high pressure and low pressure
6. Refrigerant pressure sensor
7. 1. Refrigerant line, front (vehicles with and without automatic rear air-conditioning system)
   2. Refrigerant line, rear (vehicles with automatic rear air-conditioning system)
8. 1. Evaporator, front (vehicles with and without automatic rear air-conditioning system)
   2. Evaporator, rear (vehicles with automatic rear air-conditioning system)

Checking sequence: 

1. Check of components 1, 2, 3a, 4, 5, 6, 7a and 8a of the automatic front air-conditioning system.

   If no fault found: 

2. Check of components 3b, 7b, 8b and connection points of the automatic rear air-conditioning system.

1. Air conditioning condenser: 

   Damage caused by stone chipping, etc. is the most frequent cause of air conditioning condenser leaks (1):

   1. Visual inspection in the area of the radiator grille (2) and air inlet grill, center (3).
   2. Check damaged points first.
   3. Check the remainder of the air conditioning condenser.

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2. Connection point capacitor - refrigerant line: 

   Check the connection point between the connection at the air conditioning condenser (1) and refrigerant lines (2).

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3. Expansion valve: 

   Check the connection point between the expansion valve (1) and refrigerant lines (2).

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4. A/C compressor: 

   Remove drive belt from air conditioning compressor.

   Check the following components on the air conditioning compressor: 

   1. High-pressure connection
   2. Low pressure connection
   3. Pressure relief valve
   4. Radial shaft seal of the magnetic clutch: Turn the magnetic clutch several times hand force during the leak detection.

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5. Filler neck: 

   Blow out the fuel filler neck (1) prior to checking.

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6. Refrigerant pressure sensor 

   Check the sealing surface between the refrigerant pressure sensor (1) and the refrigerant line (2).

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7. Refrigerant lines: 
   1. Perform visual inspection
   2. Check damaged points first.
   3. Check bending points at points marked with an arrow. Leaks occur especially frequently at these points.
   4. Check the remainder of the refrigerant line.

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8. Evaporator: 

   Remove the center fresh air grille.

   Compliance with the following settings is absolutely  required:

   • Recirculated-air mode On
   • Lowest blower speed
   • Lowest temperature
   • Set the air distribution to ventilation (air may only flow out of the center fresh air grille)

Position sensor head (1) in air duct of middle fresh air grille (2) as illustrated and shift slowly from inside to outside above and below air flap (3). Carry out this operation on the left and right fresh air grilles.

In this case the expansion valve must be covered!

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Following the completed leak detection: 

• Evacuate and fill heating and air conditioning system. Refer to: SUCTION, EVACUATING AND FILLING AIR CONDITIONING (R134A)  or SUCTION, EVACUATING AND FILLING HEATING AND AIR CONDITIONING SYSTEM (R134A)  or SUCTIONING, EVACUATING AND FILLING HEATING AND AIR CONDITIONING SYSTEM (R1234YF) .