Few pointers for anyone wanting to retrofit rear electric seats + heating

[Ronin]

I have recently retrofitted rear heated and electrically adjustable seats to a car that has never had any of this from the factory.

Here are some of my findings and pointers:

1. When buying seats make sure they have airbags in them if you have a FL car, if you have a prefl it doesn't matter so much.

2. Don't even attempt this without at least connector cut-offs of the loom, circuit diagram pdf's from the forum and some electrical knowledge

3. You will have to dismantle the whole interior, and by this I mean removing front and rear seats, center console and carpet to run the wiring the factory way which is like this:



4. If you picked electrically adjustable seats, make sure the headrests adjust and if not fix them before installing in the car.

5. Electric headrests are also supposed to retract at the press of a button above the head unit and there's a relay trigger wire for that. With a modern head unit with a reverse camera that's not required, so I have it wired to * of my driver seat memory switch, which also operates the passenger memory, so basically with one press of a button, you put the whole interior into its default position, so passenger seat moves to match driver seat position, and headrests move down.

6. New fuses need to be added for heat and electric movement. I used 2x 20A fuses (I used separate fuses for adjustment and head), the fuse holders are the same ones as for Bose, so i gut cut offs of these from Ebay and one of forum members

They look like this:



They live here:



And plug into the fuse distribution like this:


Lastly the seat heat adjusters:

They need constant 12v from the new extra fuse added
They need illumination wire connected so they light up at night,
ground
switched ignition to turn them on and more importantly off when you leave the car
they also receive temperature sensor feedback from seats and send the signal to actually heat the seats.

You will only need a new wooden trim and the heat adjusters, the plastic frame behind which sits under the rear vents already has the holes for them:




And lastly, don't cut corners, crimp and terminate wires properly, budget around 10-15h if you have bits off loom but not the whole thing, and around 8 if you have a complete loom, all labelled and out of the car.

[Ronin]

Also my loom was very incomplete

Luckily MJ let me use her loom for copying.

MJ's loom on the left, mine on the right



And this is what we had to go though to extract it:




Finished product:



I couldn't have done it without MJ's help, or i would be in my 50's by the time i figured it out:ROFL:

[Fabio.Vieira]

Hello Ronin.

I'm trying to do something similar but with the front seats, my original didn't have front heated seats.

I've already bought some fully electric seats with heating and control buttons.

My car does not have the necessary wiring to install the heated seats, I have to manufacture it.

This is where I need help, I don't know where to start. Maybe an electrical scheme for the frontal seats would be a good help.

Thanks

[Ronin]

Hi Fabio

The best way to go about this (and I would do it if I could go back in time) is to find a donor car at a scrap yard or wherever, and carefully remove the loom from it, taking a lot of pictures of where all the wiring goes, and where it connects etc.

I was lucky because a friend of mine (MikkiJayne) had a spare loom i could borrow for a few weeks and copy.

It is possible to manufacture a loom just from the diagrams, but the diagrams will not tell you how long every cable has to be to reach where it needs to go, so it would be a very slow and 'hit and miss' process.

In the electrical section there is a wiring diagram for front electric and heated seats.

[MikkiJayne]

Definitely find a donor to get the harness from. If you follow the wires back from the seat connectors, you can find each junction where the seat heating is joined to the main harness. You can then split the heated seat wires out, labelling each junction as you go which gives you a separate seat harness which you can the put back in your car. Almost always, your car will have a junction in the same place for each wire so you can then splice your new seat harness back in to your car in the same way the factory would have done it. Same fuses, same wire locations etc. This is by far the easier way to do it compared to trying to build a harness from scratch.

I've done a bunch of retrofits like this. Once you get in to it, this is the easiest way to do it. You don't even need to know what the wires do really, only where they came from in the donor, and put them back there in yours. You do need to account for differences between PF and FL though. Some things are the same in both, but most things are different, definitely seat heating.