64 50 ... Troubleshooting by pressure measurement (R 134a)

WARNING: This page is about a different car, the 2006 BMW X5, 2005 BMW X5, and 2004 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.

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.

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.

Fig 1: Identifying Normal Inlet Pressure And High Outlet Pressure

Courtesy of BMW OF NORTH AMERICA, INC.

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

Remedy:

REPLACE COMPRESSOR .

Fig 2: Identifying High Inlet Pressure And Low Outlet Pressure

Courtesy of BMW OF NORTH AMERICA, INC.

Compressor does not run with equal inlet and outlet pressures.

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).

Fig 3: Identifying Unequal Inlet And Outlet Pressure

Courtesy of BMW OF NORTH AMERICA, INC.

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

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, check expansion valve for unobstructed throughflow; replace if necessary. Refer to HEATING AND AIR CONDITIONING - TECHNICAL DATA .
Then evacuate and refill A/C system. Refer to 64 50 009 DRAWING OFF, EVACUATING AND FILLING A/C SYSTEM (R 134A) .

Fig 4: Identifying Normal Inlet Pressure And Low Outlet Pressure
Courtesy of BMW OF NORTH AMERICA, INC.

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

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.

Fig 5: Identifying Low Inlet Pressure And High Outlet Pressure
Courtesy of BMW OF NORTH AMERICA, INC.

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

Remedy:

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

Fig 6: Identifying Low Inlet Pressure And High Outlet Pressure

Courtesy of BMW OF NORTH AMERICA, INC.