Audi A6 - noise on starting

[marksg]

For the last couple of weeks, when starting our Audi 1999 A6 4.2, there is a high pitched squeal for around 30 seconds. If you turn off the engine and wait until the squeal stops, then restart, the engine sounds normal. It only does this in the morning - particularly when it's cold, and is fine the rest of the time. At first I thought it may be something to do with the air-con compressor; it's definitely not just the fan belt slipping. It sounds as though a fan/motor is shutting off when the noise stops. Any ideas?

[parrot of doom]

Have you tried starting it with the climate off?

[marksg]

Even if I switch the climate control off, the noise continues - it's coming from the drivers side of the engine bay, low down and towards the front - after around 30 seconds, you hear a click, the roar of a fan or similar winds down, and the screaching noises stops with it. Can't see what's causing the noise just by looking around engine bay.

[agent006]

Starter motor not disengaging properly?