unstoppable fan draining battery on Caravelle t5 130hp 2008 lhd

Hi guys, First post as noobie.
Have a t5 Caravelle 2008 tdi, 130hp, that has 160,000km (100,000 miles) on the clock.
During the winter months with temperatures below zero a fan in the engine bay area
refuses to turn off after the ignition is turned off and the key is removed.
In the morning of course the battery is flat.
Have had the van into VW workshop several times but still no joy.
They have changed sensors and the problem seemingly disappeared
but after a few weeks returned.
Can anyone come with suggestions I can present to VW to get them
thinking out of the box?

Thanks in advance, graybeard

Sounds like the auxiliary water pump running on due to the auxiliary coolant heater running to help the engine reach normal operating temperature - usually this happens at temps below 5C. Do you know which sensors have been changed? I believe there are a few related to coolant temperature. One will be responsible for stopping the pump.


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