If your HVAC system's blower fan is running after shut down, or operating erratically...then it's probably the cause of your battery drain. The FSR/FSU controls this operation. But don't confuse the FSR/FSU and the HVAC's blower fan with the little fan inside the IHKA control panel. These are two different components with two different functions & purpose.
Quote:
Originally Posted by mcurcio1989
...This does bring up an interesting question. What exactly does the GM control?? I know it controls a lot of the locking functions but anything else?
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You can get an idea of what the GM controls in the topology chart below. The IKE (instrument cluster electronics) is the considered the "main gate-keeper" since all of the communication buses run to it or thru it:
TIP:
- FZV = central locking system (as well as FBZV - remote central locking)
- DWA = anti-theft alarm siren system
As other's mentioned, the faint sound you hear after turning the vehicle off is probably the little fan inside the IHKA unit. It draws air into the vent on the left side of the IHKA across a thermistor which is how the IHKA regulates & maintains the air temp you have set.
This little fan is on the P-bus which is a low command bus...and there are certain components that remain active until the car goes into SLEEP mode...or become active when the car WAKES.
To check the little fan in the IHKA...as others already mentioned, you need to check back 16 minutes after shut down of the car.
BUT YOU CAN NOT LIFT A DOOR HANDLE OR PRESS A BUTTON ON THE REMOTE...if you do, then you WAKE the vehicle up again, thus starting-up the little fan again. You'll need to roll a window down, or remain inside the car touching nothing for the requisite time interval.