A/C - Common Complaints
Group 64
Heating and
Air Conditioning
Bulletin Number
64 03 98
Woodcliff Lake, NJ
April 1998
Product Engineering
SUBJECT:
E39 Integrated Automatic Heating and Air Conditioning System (IHKA)- Common Complaints
Model:
E39, 5 Series
Situation:
Warranty analyses of the returned IHKA Control Modules, indicate that a substantial percentage of the replaced units do not exhibit any signs of
malfunction. The reasons for replacement were: misdiagnosis or unfamiliarity with features of IHKA system.
Listed below are the most frequent complaints pertaining to the IHKA system:
Complaint 1:
"The A/C system delivers air-conditioned air after a delay of approx. 5 minutes".
Cause:
The IHKA Control Module is either not coded or has been coded incorrectly.
Action:
Recode the IHKA Control Module using ZCS Coding/Recoding/IHKA path.
Complaint 2:
"The A/C compressor runs constantly when the A/C is switched on".
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Cause:
The E39 IHKA system uses a variable displacement A/C compressor. Since output is regulated internally by the position of the swash plate,
compressor cycles less often.
Action:
Normal operation mode of A/C compressor.
Information regarding compressor operation can be found in the DIS/MoDiC under
"Functional Description:-Air conditioning and Compressor control", or in E39 IHKA Training Reference Manual.
Complaint 3:
"The interior temperature sensor runs constantly".
Cause:
The interior temperature fan located in the face plate of IHKA Control Module is required to ensure accurate temperature measurement. This fan is
switched off by means of the load cutoff function 16 minutes after the ignition key is removed from the ignition lock. The fan is switched back on,
when one of the vehicle doors is opened. This gives the impression that the fan is running constantly.
Action:
Normal operation mode of the system.
Information regarding interior temperature fan can be found in the DIS/MoDiC under "Functional Description-Temperature Control".
Complaint 4:
"Footwell is heated sporadically".
Cause:
If the center stratification adjuster is set to max. cold position and the air vents are pointed downwards, the cold air flow is directed towards the
interior temperature sensor. That causes the IHKA Control Module to detect low temperature. The IHKA tries to compensate and to "heat up",
particularly at the area of footwell outlets.
Action:
Customer has to be informed about optimal position of the stratification adjuster. Information regarding front mixing air control can be found in the
DIS/MoDiC under "Functional Description-IHKA Temperature Control".
Complaint 5:
"The heater blower only runs at a constant speed, increases its speed on its own or stops running from time to time while in manual mode".
Cause:
The faults may be found at the following components: blower output stage, blower relay, blower motor, power supply, control voltage output at the
IHKA Module.
Note:
The blower output stage is not diagnosis-capable. Malfunctions in the blower output stage, relay or motor are not being stored in the IHKA fault
memory. Therefore, the fact that there is not entry in the fault memory doesn't indicate that a fault is not present in one of the above components.
Only faults in blower control voltage output from the IHKA Module are entered into the IHKA fault memory.
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Action:
Troubleshoot using DIS or MoDiC.
Complaint 6:
"Different versions of the IHKA have been modified several times since the introduction of the series. For a description of function features refer to
Technical Reference Information 64 75 98 from January of 1998.
