Advice needed - Jet powered coolant fan!

[Varrick]

Hi all,

New member of this great community!

I have a 2003 D3 4.2 petrol which I have had now for a few months, but without it's problems, and very grateful for advice to help the old girl get back on her feet!

Battery - appears to be a drain, 10% battery indicator on MMI, starts up ok, but convenience functions such as central locking appear not to work, until after the car has been running. Lock the car via remote, go back to it after 10 mins same thing again.

Coolant fan 2, start the car up from cold 10 seconds later, sounds like a 747 on take off, with larger (not AC fan) on full chat, continues even when engine switched off, drained the battery very quickly so had to pull the connection to stop it. AC fan cooling fan works fine, activating / deactivating with AC on and off as expected.
Hooked up to VCDS and reports 18308 - Coolant Fan Control 2 P1900 - 004 - Open or short to ground. initially thought may be control unit integrated into fan, but tested by independent state ok, and that think the problem is somewhere else up the circuit.

Other issues which may or may not be related are no siren when alarm goes off, advanced key not working, electrical steering column adjustment not working.

Apart from that all good!

Any advice or guidance greatly appreciated, as is a copy of a wiring diagram to help diagnose the coolant fan fault?

Thanks in advance guys!

Varrick