4.2 tdi hot start problem

[velour]

Hi all,

Having an ongoing issue with my 2010 (D4) 4.2 tdi and thought I'd ask if anyone has any ideas.

Issue is that it starts from cold no problem, runs fine and happy for 2+ hours on the motorway. However, as soon as I stop there is a high risk that the engine management won't let the engine start again.
The engine fan starts going at max and when the start button is pressed alomst every fault code displays on the dash in sequence (ESC, TPMS, air suspension, diff etc) and the car won't start.
However, as soon as the fan stops everything is OK and the car will start, but the hotter the external temp the longer it takes the fan to stop.
It's also the case that, if the car is hot, just firing up the electrics (e.g. opening a door) will cause the engine fan to come on even if it had stopped previously.
Recently it's been running the fan so much it flattened the battery.

VCDS doesn't reveal anything so wondering if it might be something to do with a temp sensor on the way out?

Any thoughts on what it might be and how to check?

Many thanks.