For example when the IHKA unit does not switch the heater valves off. Turn on driver side the tmeperature wheel of the IHKA control to max., that shuts the power supply to the heater valves of both sides off, that is the emergency function. If the drain now drops, it is the control module or the control panel.
You could also unplug from the IHKA control module one after the other of the 4 plugs. And measure the drain , if it changes, you are closer to it.
Do a search "IHKA pinout shogun" there I have mentioned all pins of the IHKA unit and the sword.

Fuse 20 on my 1988 is for:
DWA, IHKA, brake line warning, central locking system, EML (that you do not have on the 740), instrument cluster, check control, OBC, park ventilation, part/tail/underhood lights (glovebox lights, tunrk lihghts etc still on?)power windows, sunroof.

So the BIG consumer is the IHKA. Also try to unplug the sword plug and see if drain changes.

E32 750iL 11/88, E32 750iL Highline 03/90
7 series Tech Tips

• Power drain fuse #20 (nt) - woolee03 2008-11-15 20:22:31 (49 views)
  • Re: Power drain fuse #20 - woolee03 2008-11-15 20:27:14 (45 views)
    • found the drain. IHKA module - woolee03 2008-11-16 13:23:00 (44 views)
      • proceed systematic in analysis (url) - shogun 2008-11-16 23:32:41 (48 views)
        • Re: proceed systematic in analysis - woolee03 2008-11-17 07:39:13 (36 views)
          • Re: proceed systematic in analysis - click 2008-11-26 16:23:05 (9 views)
          • when you open the IHKA control module (url) - shogun 2008-11-17 09:48:36 (50 views)
    • IHKA is always a possibility - shogun 2008-11-15 21:26:51 (81 views)