Folks--
At 170K miles, I finally replaced my Heater Core. Turns out it wasn't actually leaking, it was just the O-Rings; However, during this adventure, I had to remove the dashboard so I could access various vents, flaps, and linkages in the system. To do so, I removed the GM / LKM / EKM / Airbag / Steering Wheel / Instrument Cluster / Glove Box and every switch and button along the way..
Now-- As many of you know, you shouldn't start/run the car without the steering wheel/airbag present or risk tripping the SRS light.
HOWEVER--
In my case, after disconnecting the battery and letting the SRS system discharge, I ALSO disconnected ALL the connectors from the SRS system under the dash.
(I figured-- why would the SRS system throw a fit if it never even knew the car was powered/started---)
To test my heater core, I started up my car with all the aforementioned things missing, I only plugged in the IHKA controls and IHKA servo motors and temperature sensors, and reconnected a battery.
I started and ran the car for 20 minutes, checked for heater core leaks, exercised various flaps, etc. I got the flaps to a place I could work on the other flaps and pulled the battery again. (BTW-- It's really eerie inside a running car without any electronics/lights/chimes)
Today I reassembled the first half; enough to drive the car to the auto parts store to get some rear-view mirror adhesive. This included minimal dash board, instrument cluster, steering wheel, airbag, SRS modules, LKM/EKM/GM trio, and the IHKA controls sitting atop the mound of cables/connectors. Connected the battery and 4-ways came on (silly crash module); so I had to find my hazard switch and connect that too..
I started the car up, SRS light came on briefly like it should, and then NO SRS LIGHT! HOORAY!
TL;DR - If you have to connect your battery and start the car without the airbag present, disconnect all the SRS stuff TOO (after allowing enough time for the SRS to discharge; 15 mins?).
I'm not sure what would happen with the EMK and/or Instrument cluster connected, but in my case, they were also disconnected and out of the car at the time.
'89 735i, '91 850i, '81 MB 380SLC (For Sale), Tesla Model 3, and VW Passat TDI -- Yes, I still repair General Modules, DM for info!
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