A/C - Humming/Droning Noises
SI B64 01 03Heating and Air Conditioning
May 2003
Service Engineering
This Service Information bulletins supersedes S.I. B64 01 03 dated May 2003.
[NEW] designates changes to this revision
SUBJECT
Humming, Droning Noises When Air Conditioning Is Switched ON
MODEL
[NEW] E46 (3 Series) with M54, M56 engine. Vehicles produced until September 2002
SITUATION
The customer may complain of a humming or droning noise in the engine speed range of 2000 - 4000 RPM. In addition at very low engine speeds, howling noises (similar to the timing chain) may occur.
CAUSE
The vibrations of the engine are transmitted into the vehicle interior through the intake pipe of the air conditioning compressor.
PROCEDURE
In case of a customer complaint, replace the intake pipe from the evaporator to the compressor. The new intake pipes are fitted with a vibration damper weight. Also on the compressor side of the intake pipe is a muffler (small expansion tank).
1. Recover the refrigerant from the air-conditioning system as per repair instructions 64 50 009.
2. Replace the intake pipe from the evaporator to the compressor.
3. Evacuate and recharge the air-conditioning system as per repair instructions 65 50 009.
4. Follow SI B64 09 93 for guidelines in reference to the Receiver Dryer.
Important:
In such cases, replacing the compressor or expansion valve will not remedy the situation.
PARTS INFORMATION
WARRANTY INFORMATION
Covered under the terms of the BMW New Vehicle Limited Warranty.