Member Since: 29 Nov 2006
Location: North Yorkshire
Posts: 15264
What is this, please.
Not got around to finding out everything in my new[to me] MY14 D4.
But just about to wire in my Blackvue I became aware of the unit in the pic.
It's sighted at the top of the windscreen, behind the mirror, drivers side.
Looking at the cut out for the cable on the headling, I don't reckon it's a oem unit.
Anybody got an idea what it is please?
Click image to enlarge
...... always on the road less travelled 🚧
18th Jun 2019 2:59 pm
BBDisco3
Member Since: 23 Nov 2008
Location: Cheshire
Posts: 3646
It is original - been mentioned on here before but I've forgotten what it is
18th Jun 2019 3:27 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26776
It’s a humidity sensor.
18th Jun 2019 3:43 pm
ronp
Member Since: 29 Nov 2006
Location: North Yorkshire
Posts: 15264
Thanks Gareth [& BBDisco3 to a lesser extent ].
So is it OEM?
And what really is the purpose of it [ok, I know ... to sense humidity], but what is triggered when humidity is sensed?...... always on the road less travelled 🚧
With a humidity sensor fitted, the ATC module controls the moisture content of the air in the vehicle. This is achieved by raising the evaporator temperature to increase the humidity of the air entering the vehicle, and reducing the evaporator temperature to reduce the humidity of the air entering the vehicle.
I should've hit the search button before posting. ...... always on the road less travelled 🚧
18th Jun 2019 4:24 pm
promitheus
Member Since: 04 Jul 2009
Location: Afidnes, Greece
Posts: 572
As said, it's the front windscreen humidity sensor.
After spending months back on 2014-15 to figure our why my air intake flap would not completely close during winter days, allowing vehicle exhaust fumes to enter the cabin during rash hour no matter how I setup the climate controls, it turned out that it was the humidity sensor that would seldom allow the flap to completely close. LR could not figure out how it worked either, sending emails to LR trying to figure this out. Finally I used my IID Tool to observe how it worked and the logic behind. Ordered a second sensor just in case the original was broken, but the flap would almost never close (except in summer or sunny days).
To keep a long story short, vehicles fitted with the humidity sensor will not completely close the air intake flap if humidity sensor reading is above 35-40%, however it takes into account things like outside temp, internal temp etc.
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]. 
