Symptom Related Diagnostic Procedures

Possible Complaints At Refrigerant Circuit

NOTE:

- A/C system is functioning correctly when a temperature of 7 degrees C or lower escapes at instrument panel air vents.
- Setting on Climatronic "LO".
- Setting on A/C system "AC" on; "max"; "cold".

Test requirements:
- On Board Diagnostics (OBD) of A/C system using diagnostic operation system VAS 5051A in "Guided Fault Finding" cannot detect any malfunction, no shut-off condition for A/C compressor is displayed in measuring value block (only in vehicles with "A/C system" OBD).

Possible complaints

NOTE:
- For all complaints marked by *.
- Total failure of cooling system.*
- 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:

A/C compressor makes noise
- Re-tighten securing bolts for A/C compressor and A/C compressor bracket using a torque wrench.
- Check routing of refrigerant pipes; 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).

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 valve for condensation water hose, it must not become stuck 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).