A/C System - Cuts Out on Light Acceleration
GROUP 64Heating and A/C
Bulletin Number
64 02 00
Woodcliff Lake, NJ
June 2000
Service Engineering
This bulletin is also issued in Group 12 (Engine Electrical), S.I. 12 05 00, the contents of which are identical.
SUBJECT:
A/C "Cut-Off" During Light Acceleration - E38, E39 with M62TU
MODEL:
E38 740iL, 740i produced 9/98 - 1/00
E39 540i, 540iA produced 9/98 - 1/00
Situation:
Customer complaint that the A/C is blowing warm air when accelerating lightly from a stop. The A/C functions properly during all other driving conditions.
Cause:
[1][2]DME/ECM calibration
Correction:
On a customer complaint basis only, reprogram the [1][2]DME/ECM with CD 21.0 or higher.
Procedure:
After verifying the complaint:
1. Check the DME control unit numbers.
2. If the numbers in the table are listed, then no reprogramming is required, but further A/C diagnosis must be performed to repair the customer complaint.
3. If the numbers listed above are not displayed. reprogram the [1][2]DME and then verify that the control unit numbers have been correctly programmed. The numbers listed above will be displayed after reprogramming with CD 21.0.
* Note:
Control unit numbers may change when new DIS software is released.
4. The new calibration will raise the A/C compressor "engine load cut-off" to 70%. The A/C compressor will still cycle off if the engine load is calculated to be 70% or greater. This A/C compressor "cut-off" will still occur, when the vehicle is accelerated hard (approximately 40 - 50% throttle application) from a full stop, to allow for maximum engine power.
Warranty Information;
Covered under the terms of the BMW New Vehicle Limited Warranty.