A/C - Changes to Control Units

90bmw20 Group 64 Heating and Air Conditioning
Bulletin Number 64 08 90 (3158)
Woodcliff Lake, NJ November 1990 Service Engineering
SUBJECT: Changes to IHKA Control Units

MODELS: 7 Series (E32)

Situation: Two changes to IHKA Control Units have taken place. The areas affected are:

1. Rear seat area ventilation control.

2. Road speed influence on fresh air flaps.

Change 1:

The stepper motor, linkage and flap for rear seat area ventilation have been eliminated as of early June (week 23)1990. Control of air volume is strictly by means of the thumbwheel at the outlet (rear of console). A disconnected wiring harness may be encountered (formerly connected to the microswitch at the thumbwheel), but it is without function and need not be reconnected.

Change 2:

The influence of road speed on the position of the fresh air flaps has been eliminated in control unit versions 02 and 03. Version 01 has this influence in the following manner:

^ Fresh air flaps 100% open, at road speeds of 0-37 mph.

^ Fresh air flap opening is reduced linearly from 100% to 40% as road speed increases from 37 to 87 mph.

^ Fresh air flaps 40% open at road speeds above 87 mph.
A slightly different form of road speed influence on fresh air flap opening is incorporated into version 4.0 control units (specific to 850i (E31)). This version is influenced by a combination of road speed and blower current, and will be explained in more detail in a separate Service Information Bulletin.

Note: Control unit version identification is possible by means of the BMW
Service Test or the MODIC. The following listing of version date ranges is only approximate and, of course, does not account for control units replaced by a later version. Always verlty control unit version wlth the BMW Service Test or MODIC when diagnosing.

Version 01 09/86 -- 09/87
Version 02 09/87 -- 12/88
Version 03 12/88 -- --
Version 04 05/90 -- --

Warranty
Status: Information Only