Possible Refrigerant Circuit Concerns

Possible Refrigerant Circuit Concerns

NOTE:
- The air conditioning system is functioning correctly when the air flowing from the instrument panel vents has a temperature of 7 degrees C or lower.
- Setting on Climatronic "LO".
- Setting on air conditioning system "AC" on; "max" ; "cold".

Test Prerequisites
- The air conditioning system On Board Diagnostic cannot determine malfunctions with the Vehicle Diagnosis, Testing and Information System VAS 5051A via "Guided Fault Finding". No shut-off condition for the A/C compressor is shown in the measured value block (only on vehicles with On Board Diagnostic "Air Conditioning System").

Possible Concerns

NOTE: With all complaints marked with *.

- Total cooling system failure.*
- Insufficient cooling performance at all vehicles speeds or engine speeds.*
- None or insufficient cooling after driving a few miles.*
- A/C compressor, A/C Clutch N25 or A/C Compressor Regulator Valve N280 are switched off by A/C Refrigerant Low Pressure Switch F73, A/C Refrigerant High Pressure Switch F118, A/C Pressure Switch F129 or by A/C Control Head E87 or Climatronic Control Module J255 due to excessive or insufficient pressure.*
- None or sharp decrease in fresh-air supply after driving several miles (evaporator iced up).*

From these, the following complaints may also occur:

The A/C compressor makes noises
- Re-tighten compressor securing bolts and compressor bracket using a torque wrench.
- Check routing of refrigerant lines; they must not touch other components and must not be subject to strain (align if necessary).

Noise (refrigerant hammer) occurring immediately after switching on air conditioner and/or when cornering or braking:
- Discharge, evacuate and re-charge refrigerant circuit (too much refrigerant in circuit).

NOTE:
- Too much refrigerant oil in the circuit may also result in this problem (no adjustment of refrigerant oil quantity, for example, on replacing compressor). With this complaint, the refrigerant circuit should be flushed with refrigerant R134a.
- The refrigerant must be drained from the A/C compressor via the oil drain plug (replace O-ring). To facilitate this, the ribbed belt pulley or magnetic clutch plate on the A/C compressor should be rotated by hand. After flushing, the entire quantity of refrigerant oil specified, should be added to the refrigerant circuit (50 grams directly in the A/C compressor).

Water sprays out of vents (in dash panel or footwell) although air conditioning system is otherwise functioning properly:
- Check proper routing of condensate drain; it must not be crushed or kinked.
- Check condensation drain valve, it must not be clogged by wax or underbody sealant and must open and close properly.
- Check plenum chamber cover; it must not be damaged and must be properly installed (to stop water running into evaporator).
- Check water drains in plenum chamber; they must not be blocked (e.g. by leaves).