64 50... TROUBLESHOOTING BY PRESSURE MEASUREMENT (R 134a)

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NOTE: The troubleshooting by pressure measurement described in the following is only possible on A/C systems with uncontrolled compressors.

This includes among others:

E53
E46M47 up to 09/2001
E38 up to 09/1997
E36, E36/7
E34
E32
E31

Connect service station to car and open both valves on the charging hoses. Adjust A/C system at control panel as described for A/C efficiency measurement. Refer to 64 50... AIR CONDITIONER TEST (R 134a) .

NOTE: The following values apply as normal pressure ranges for ambient temperatures between + 20°C and + 40°C:

Inlet pressure: 1.0 - 2.2 bar
Outlet pressure: 12 - 22 bar

Normal inlet pressure and high outlet pressure indicate an overfilled system, a contaminated condenser or a faulty auxiliary fan.

Fig 1: Identifying Normal Inlet Pressure And High Outlet Pressure

Courtesy of BMW OF NORTH AMERICA, INC.

Remedy:

Draw off, evacuate and refill A/C system. Refer to 64 50 009 DRAWING OFF, EVACUATING AND FILLING A/C SYSTEM (R 134A) . Clean condenser from outside, check auxiliary fan, replace if necessary.

High inlet pressure and low outlet pressure indicate a faulty compressor.

Fig 2: Identifying High Inlet Pressure And Low Outlet Pressure

Courtesy of BMW OF NORTH AMERICA, INC.

Remedy:

Replace compressor.

Compressor does not run with equal inlet and outlet pressures.

Fig 3: Identifying Unequal Inlet And Outlet Pressures

Courtesy of BMW OF NORTH AMERICA, INC.

Remedy:

If the anti-icing facility has shut down the compressor, check evaporator sensor and power supply to clutch. Otherwise check clutch mechanically (by slipping).

Normal inlet pressure and low outlet pressure indicate an insufficient fill quantity of refrigerant.

Fig 4: Identifying Normal Inlet Pressure And Low Outlet Pressure

Courtesy of BMW OF NORTH AMERICA, INC.

Remedy:

Draw off and measure refrigerant. Refer to 64 50 009 DRAWING OFF, EVACUATING AND FILLING A/C SYSTEM (R 134A) .
If the amount drawn off corresponds approx. to the specified fill quantity (680 +/- 10 g), check expansion valve for unobstructed throughflow; replace if necessary.
Then evacuate and refill A/C system. Refer to 64 50 009 DRAWING OFF, EVACUATING AND FILLING A/C SYSTEM (R 134A) .

Low inlet pressure and high outlet pressure can be caused by a variety of factors:

Fig 5: Identifying Low Inlet Pressure And High Outlet Pressure

Courtesy of BMW OF NORTH AMERICA, INC.

Icing of evaporator
Remedy: Check evaporator sensor, replace if necessary.
Obstruction on H.P. side after condenser or on L.P. side

Remedy:

Check drier, expansion valve and pipes in these areas for unobstructed throughflow; clean or replace if necessary.

Low inlet pressure and high outlet pressure indicate an obstruction in the condenser area.

Fig 6: Identifying Low Inlet Pressure And High Outlet Pressure

Courtesy of BMW OF NORTH AMERICA, INC.

Remedy:

Check condenser for unobstructed throughflow; clean or replace if necessary.