So, I tried your trick, pulling out the 40A fuse on the driver's side at the top of the fuse panel, cuts power to the AC/blower fan. I charged up the battery and got the VW running.
I then plugged in my Ross-tech VCDS and cleared out all the fault codes because my battery had run dead and set off a ton of irrelevant low voltage fault codes. I restarted the VW and then checked for fault codes again and found the following:
Address 08: Auto HVAC Labels: 7L6-907-040.clb
Control Module Part Number: 7L6 907 040 AD
Component and/or Version: CLIMAtronic R/L 4326
Software Coding: 0020030
Work Shop Code: WSC 31414 790 00001
1 Fault Found:
00353 - Function Return Message from Fresh Air Blower Regulator
001 - Upper Limit Exceeded
Voltage: 13.50 V
Voltage: 6.05 V
Voltage: 11.77 V
Voltage: 14.00 V
I found SSP301 The Touareg heating/air-conditioning system
I have the 2C-Climatronic system.
My thought was that the Sender for blower control, front G462 (Bitron) may be going bad but, page 73 in SSP301 states:
"The sender for blower control is activated by the Climatronic control unit using a pulse width modulated signal (PWM). Power is supplied to the control by the Climatronic control unit J255. According to its demands, the sender regulates the blower motor in the air-conditioning unit."
Effect of drop-out:
"If a blower is defective, the entire heating and cooling function of the air-conditioning system fails. The diagnostics can be used only indirectly to localize a fault on the blower control unit or on the blower. For this purpose, there is a resistor in the blower control unit; this is connected with the minus pole of the blower motor. Due to this arrangement, the control unit receives ”acknowledgement information”, which can be used to determine whether the fault is at the sender, at the blower or both. There is no direct indication for a fault on the control or on the blower. However, the voltage signal of the resistor in the blower control is not a signal for the actual voltage on the blower motor, but rather a signal with which the Climatronic control unit can ”observe” the behavior of the sender for the blower control."
So, that being said, I don't know if the fan running all the time necessarily means that the G462 is bad, but power is still somehow getting to the blower fan even when the ignition is off. I know there is a feature on the car which allows the fan to run when the car is off, it is the Residual Heat Function (REST) but it usually operates at a reduced blower fan speed to prevent the battery from running down too much so I don't think that is the problem.
Back in the summer my fan quit working for a few weeks and it has been making sounds for the past year or so. I also noticed, during this latest vehicle startup, a slight hot electrical wire smell after the VW had been running a few minutes. I think my fan motor is at the end of its life and I am going to start by replacing it Part#7L0-820-021-Q (right hand drive). If that doesn't do it I'll replace the G462 (Bitron) Part#7L0-907-521-B