Hello, despite a second battery relayed on permanent positive in the trunk of the truck, the td6 struggles to start on cold mornings. A hint: the blower often starts on its own in the morning (although I turned it off the night before) when I start the engine ... any ideas ??

Could well be a faulty Final Stage Resistor, the component that controls the blower fan speed. Common problem causing battery drain.
If you do a search on here, plenty of information.
You could try removing fuses F12 10A and F34 7.5A and see if the problem goes away.
These fuses provide supplies to the FSR.

I had changed the hedgehog last year ... not easy ... but thanks for the tip: I start with the fuses and I'll see !!

Hi, you were right: it's the fsr that fails ! I am disappointed by the short time that my replacement hedgehog has worked... : an idea or advice about the brand of the new one that I'll order ?

IIRC the original was a Bosch...  Pete

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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
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I had 3 drains on my RR (look for my older posts as cant remember what they were). 1 was FSR, one was the BCU and cant remember the 3rd, maybe headlight washers?

Just found a reply from NICEDAYFORIT who was a huge help, this i his words:

Fuse 28 headlight washers/wipers
Could be a faulty headlight washer/wiper relay allowing current to pass.

Fuse 27 glove box light, interior lights, windscreen washers and analogue clock. All common to BCU.


Fuse 12 ac and heated front seats. Supplies ac blower motor.
Almost certainly faulty FSR.