A/C Controls - Blows Warm Air On Light Acceleration

GROUP 12
Engine Electrical

Bulletin Number
12 05 00

Woodcliff Lake, NJ
June 2000
Service Engineering

This bulletin is also issued in Group 64 (Heating/Air Conditioning), S.I. 64 02 00, the contents of which are identical.

SUBJECT:
A/C "Cut-Off" During Light Acceleration - E38, E39 with M62TU

MODEL:
E38 740iL, 740 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:
DME/ECM calibration

Correction:
On a customer complaint basis only, reprogram the DME/ECM with CD 21.0 or higher.

Procedure:

After verifying the complaint:

1. Check the DME control unit numbers.

2. If the following numbers are listed, then no reprogramming is required, but further A/C diagnosis must be performed to repair the customer complaint:

Basic control unit Vehicle Programmed Control Unit
7506366 540i 7506506*
540iA 7506514*
540iA Sport 7506516*
540iAT 7506524*
740i/iL 7506554*
740iL Sport 7506556*

3. If the numbers listed above are not displayed, reprogram the DME and then verify that the control unit numbers have been correctly programmed. The numbers listed above will be displayed after reprogramming with CD21.0.

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% 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.

Note:
The following explanations will spell out the correct use of the work times.

Main Work:

Use this labor operation number when the only repair performed is the listed warranty repair.

OR

+ Associated Work:

Use this labor operation number when other repairs or services are performed along with the listed warranty repair.

Under no circumstances should both labor operation numbers be claimed. Attempts to claim both times will result in an unnecessary delay in claim processing and payment.