A/C - Blower Speed Limited to 50 Percent or Less
SI B 64 20 05Heating and Air Conditioning
December 2005
Technical Service
SUBJECT
Blower Speed Cannot Be Adjusted Above 50 Percent
MODEL
E90, E91 (3 Series)
SITUATION
With the vehicle running, the blower speed does not change when adjusted above 3 bars on the IHKA panel. The rear window defogger and the heated seats may not work. The blower does go to full speed when the front windshield defrost button is pressed.
CAUSE
Electric Load Reduction function of the Power Management system has been activated for one of the following reasons.
^ Alternator output has been fully utilized.
^ The battery charge status is in a critical state.
PROCEDURE
1. Start the vehicle and run at idle speed. Turn all electric loads off on the vehicle.
2. If the blower motor now works properly then this is considered normal system operation.
3. If the blower motor still does not function properly, perform a short test on the vehicle. Refer to SI B61 08 00 for troubleshooting closed Circuit Current measurement problems.
4. Complete test plans for any Power Management faults that are stored in the DME. Hint: note environmental conditions for any Power Management faults that are stored. For example: DME FC 2DEB "Power Management vehicle electrical system"
^ Engine Speed: 1088 RPM
^ Voltage Term 87: 14.34V
^ Battery Voltage measured by IBS: 9.23 V (low voltage may indicate a faulty IBS Intelligent Battery Sensor if the other environmental conditions are correct).
^ Generator nominal Voltage: 14.4V
5. Test the battery and the charging system using the BMW Battery Tester per S.I. B04 25 02 and correct as needed.
6. If the system still does not work properly replace the battery sensor.
7. Clear all stored faults from the system and retest.
WARRANTY INFORMATION
Covered under the terms of the BMW New Vehicle Limited Warranty.
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