General info on heated steering wheel
 

In this thread I will share some knowledge on heated steering wheels in D2's.

There isn't a lot of info about how they work and what parts need to be sourced so here are the basics:

How to tell if you have a heated steering wheel?
If you put drivers seat heating on and your wheel gets warm as well you have a heated steering wheel.
They only came in 4 spoke wheels and unlike the seats, there's only on and off control for the heat, as soon as you put your heated seat on 1, the wheel fully heats up. Both FL and Pre-fl cars came with heated wheels.

How to tell a non heated steering wheel from a heated steering wheel when looking for one?

You will see extra wiring coming out of the bottom left spoke of the 4 spoke wheel(bottom right on FL1 wheels).
The green or sometimes blue wires are the temperature sensor wires, whereas the black wires are the power wires for the heating element.
You can easily check if a heated steering wheel works out of the car by doing a continuity test on the 2 pins of the black heating element cable, if there's no continuity, its 100% broken.

https://i.imgur.com/CTESszM.jpg

The other part of the heated steering wheel system is the clock spring, its a special clock spring with extra wires going to and from it as well as slip rings because a normal flex cable inside can't carry the current.

Front pic of a heated clock spring with extra wiring for heat power:
https://i.imgur.com/LpOstbu.png

Back of a heated clock spring, notice the extra 2 pin connector:
https://i.imgur.com/U2whBY1.png

This picture shows a heat clock spring for a pre-fl car, notice the extra wires at the top:
https://i.imgur.com/IncsvFx.png

This is what the slip rings and brushes for heating look like:
https://i.imgur.com/ULyQP9p.png
https://i.imgur.com/hpOeozz.png
And the 2 brushes:
https://i.imgur.com/Z3BvBMB.png

The temperature sensor is a negative thermal coefficient thermistor, meaning the resistance goes up as temperature goes up non linearly and that's what controls the heating element and ensures it won't overheat.

It looks like this:
https://i.imgur.com/afvaIJD.png

And lives roughly here:
https://i.imgur.com/JAJmh6R.png

The heating element lives under a layer of roam, which is under the leather of the wheel. It's basically a thin wire spread across the wheel in a zig-zag pattern, it goes all around the wheel, and even on the spokes, so no matter where you touch the wheel it will be warm.

Pictures of the heating wire:
https://i.imgur.com/FXFDLom.png
https://i.imgur.com/NTxRmLt.png
https://i.imgur.com/cl1CFtS.png

This picture shows a bare wheel with the heating element removed, you can still see the pattern though:
https://i.imgur.com/TV3eiRR.png

Is it possible to make a 3 spoke heated steering wheel? I'd say yes although it won't be cheap.
:)

That I am up for.
If anyone was to offer this upgrade...