Door mirrors & mystery stud - Altea Ego
Here is a thing that has been puzzling me. On my scenic, the passenger door mirror had a visible plastic stud on the bottom of the housing that appeared to eminate from inside the housing. My Laguna has one on the drivers door mirror, and moves when you push it. Just parked next to an Alfa, and that has a stud on the passenger door mirror.

What are they? always on the bottom and only on one mirror
Door mirrors & mystery stud - MS
Some Citroen XMs have a small lump on the underside of the passenger door mirror. Its the external temperature sensor.

Could be the same on Scenics, Lagunas and Alfas.
Door mirrors & mystery stud - HF
Was going to ask where I could get a mystery stud from, but I see I had the wrong end of the stick ;)
Door mirrors & mystery stud - Malcolm_L
Or possibly the right end once and developed a taste for it?
Door mirrors & mystery stud - HF
LMAO! - possibly, Malcolm, possibly ;))
Door mirrors & mystery stud - Altea Ego
Some Citroen XMs have a small lump on the underside of
the passenger door mirror. Its the external temperature sensor.
Could be the same on Scenics, Lagunas and Alfas.


Yup
Possible, but wouldnt it be in the airflow and give an inaccurate reading?

I had a brainwave and thought reciever aerial for the remote locking.
Door mirrors & mystery stud - Jonathan {p}
Airflow won't make a difference to the temperature it reads. Only direct sun will affect it, and it should be in the shade, hence the reason why it is put at the bottom of the mirror.

Jonathan
Door mirrors & mystery stud - Clanger
On the Synergie, it's definitely the external temp. sensor - a small lump on the underside of the passenger door mirror.
H.
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Stranger in a strange land
Door mirrors & mystery stud - Altea Ego
Blimey concencus - must be right!
Door mirrors & mystery stud - frostbite
Consensus would be right.
Door mirrors & mystery stud - SkyMan
Consensus definitely right - Clio's have this blob and its the external temp sensor.

I know this because my wife's Clio was delivered with LHD mirrors (there is a difference, apparently) and the temp sensor didn't display anything until they swapped mirrors to RHD ones.
Door mirrors & mystery stud - Altea Ego
Yup its the temperature sensor. Tested it by putting my hand over it and watching the temperature display rise.

Door mirrors & mystery stud - SjB {P}
Current generation Volvos such as my V70 also have the external temperature sensor mounted in this way.

Door mirrors & mystery stud - Andrew-T
Most cars - even Lagunas - move when they are pushed .. :-)