Automatic A/C Control Unit - Modifications
91bmw01
Group 64 Heating and Air Conditioning
Bulletin Number 64 03 90 (3070) Page 1 of 3
Woodcliff Lake, NJ January 1991 Service Engineering
This Service Information Bulletin supersedes S.I. 64 03 90 (3070) dated July 1990. It adds to the Parts Information section.
Please remove and discard S.I. 64 03 90 (3070) dated July 1990 from your S.I. binder.
SUBJECT: IHKA - "Redesign II"
MODELS: E32 (all so equipped)
Situation: A number of modifications have been made to the overall system of the automatic heating/air conditioning as of 1/89. These modification (designated "Redesign II") affect the control unit and the control panel assembly.
The Redesign II system contains improvements with regard to current consumption, operating noises, and reduction of window fogging.
Parts
Information: Description Part Number
Control Unit 64 11 8 390 000
Control Panel Assembly 64 11 1 390 811
Note 1:
The new control unit is displayed as "Version 3" during diagnosis with the BMW Service Tester.
THE VERSION 3 CONTROL UNIT IS FULLY COMPATIBLE WITH ALL PREVIOUS IHKA SYSTEMS. THE CONTROL PANEL ASSEMBLY DOES NOT HAVE TO BE CHANGED IF A VERSION 3 CONTROL UNIT IS INSTALLED IN AN OLDER VEHICLE.
Note 2:
The current Parts Microfiche (P/N 01 01 9 770 717, dated 8/90) identifies the heater control panel assembly by part number. It is, therefore, possible to select the appropriate frame and determine individual part numbers.
Select the frame of the microfiche which pertains to each control panel assembly in the event of the need to order an individual part of the assembly. The part number of the control panel assembly is printed on an adhesive label attached to the back of the assembly.
General
Information: MODIFICATION TO THE CONTROL UNIT
1. Rear Window Defogger
A) The rear window defogger switches off automatically after an operating period of 30 minutes. During this period, the defogger operates as previously, with a "fast melt" time of 10 minutes, followed by "modulated operation" (modulated operation = 40s ON, 80s OFF)
B) The detection of the fault "rear defogger -short to B - or break" is no longer recognized by the control unit as part of fault diagnosis.
REASON: As of 9/88 for the E32 and 2/89 for the E34 (Euro. version), the rear window defogger can be activated only with the engine running (power for rear defogger relay is from KL16 relay in power distribution). This would mean that the above mentioned fault would be recognized each time the ignition is switched ON with the engine not running.
2. Activation of Stepper Motors
When the ignition is switched OFF, the flap motors are set to defrost configuration. This procedure, known as "positioning sequence", is modified so that the stepper motors are now activated on after another at an increased stepped speed. This measure considerably reduces the noise level of the stepper motors.
3. Compressor Control
The compressor can now be switched on independently of cold-start interlock (by means of either A/C or recirculation buttons).
This modification helps prevent the initial "fog-up" of the windows which can occur immediately after starting the vehicle.
4. Blower Control
The blower motor operates at the lowest speed when the air volume wheel is set to the "O" position, for as long as cold-start interlock is active for the first time (cold-start interlock "ON" status displayed in diagnosis). When cold-start interlock switches to the "OFF" status, the blower is switched OFF.
This function can be returned to only after the ignition has been switched OFF and the "positioning sequence" of the control unit is complete.
MODIFICATION TO THE CONTROL PANEL ASSEMBLY
With the new control panel assemblys, the water valves are now supplied with power via KL30. When the ignition is switched OFF, the water valves remain closed until the "positioning sequence" is complete. This measure prevents heat surges after short breaks in driving.