Erratic Operation, Fault Code 52 (Fresh Air Motor) Set
Group 64Heating and
Air Conditioning
Bulletin Number
64 04 93 (3747)
Woodcliff Lake, NJ
May 1993
Product Engineering
SUBJECT:
IHKR Fresh Air Stepper Motor, Fault Code 52
MODELS:
E36
Situation:
The IHKR control module version 10.0 or earlier may cause a failure of the fresh air flap stepper motor. Fault code 52 is set in the IHKR control module.
Complaint:
Complaints vary from not being able to switch the air conditioner on/off, LED indicators on the IHKR front panel turning off suddenly, or the recirculation control stuck permanently ON or OFF.
Cause:
Some IHKR control modules may have a defective, failed motor driver circuit which leaves one winding of the stepper motor ON continuously, eventually causing permanent internal damage to the stepper motor. In that case, the complaints are a result of the failed stepper motor, but the root cause is a defective IHKR control module.
Correction:
If fault code 52 is found stored in the IHKR fault memory, the fresh air stepper motor should be disconnected and checked with an ohmmeter. (This stepper motor is located on the right side of the IHKR housing.) The resistances between Pins 5 & 6, 5 & 4, 5 & 1, and 5 & 3 should all be about 25 ohms. If any of the windings are open or shorted, the stepper motor must be replaced. In addition, replace the IHKR control module. Later version control modules have a revised motor drive circuit.
Part Information:
E36 IHKR Control Module (Version 16 or later) 64 11 8 391 512
Fresh Air Flag Stepper Motor (Blue label) 64 11 8 350 081
Warranty Status:
Parts and labor covered under the terms of the applicable BMW New Car Limited Warranty.
Defect Code: 64 11 23 02
Labor Operation: 00 50 129 Replace Control Module
Labor Allowance: 4FRU
Labor Operation: 64 11 193 Replace Stepper Module
Labor Allowance: 5FRU