Chance Hales

I recently posed the question about installing 987/997 2-way, heated sport seats in a 996 that came with the multi-way, heated, memory seats. It appeared as though no one had done the swap before, and while it may sound straight forward, it isn’t. There is some wiring involved since the plugs/pigtails on between the two cars are different, so they are not simply plug and play. On top of that, the wiring in the car is not the same left to right so once you’ve done one side, you can’t simply copy what you did for the other side (although I imagine if you don’t have memory seats they will be a lot more similar but I cannot confirm that). This write up will go through how to do it.



The first thing you need to know is this job requires cutting and splicing/soldering wires. Another observation I made after getting them installed is the seat backs are taller than the 996 seats so to get into the back you have to pull the seat back down before sliding the seat forward, otherwise it won’t be able to fold forward due to hitting the headliner. The good news is the seats actually sit LOWER in the car and there seems to be more forward and back motion on the tracks giving you more legroom and believe it or not is actually easier access to the back seats.




I recommend starting with the passenger side. It is faster and if you run out of time or need to go somewhere, you can at least still use the car. First, you’ll need to identify the wires on the 987/997 seat. On the main pigtail, the two spade connectors for pins 8 and 13 are for the seat heaters. The unlabeled pin and 9 are for the seat back. Brown is ground, red is positive. Before removing them, label both pairs of wires. Once labeled, cut them from the pigtail. The gray pigtail you can ignore. It is for the airbag and/or seatbelt, don’t remember which. You’ll be reusing your 996 seat belt latch and wiring. Nothing special is required there beyond routing the wiring and bolting the latch onto the seat. You MUST reuse your old latch so you don’t get an airbag fault code/light on the dash.





Next, remove your seat and you’ll need to do identify the wires needed from it. Before you unplug anything, DO NOT put the key into the ignition until you have plugged everything back in to avoid an airbag light. On the seat harness, one side of the pigtail has two sets of brown and red wires, while the other side has several of different colors. The middle set of red and brown is for the seat adjustments while the double brown and single red/purple stripe is for the seat heater. Give yourself plenty of extra wire and cut the red and brown wires for the seat adjusters.





Next, there is a relay on the bottom of the seat. You will need this and the associated wires. It is a single harness with two pigtails coming off it that go to the seat heaters for the bottom and lumbar. The other side is the red/purple stripe and double brown wires off the pigtail. Unplug the two pigtails and pull the relay out as one harness. Cut the two smaller pigtails off that you left on the seat, again giving yourself plenty of extra wire. Take the pigtail with the red and white wire and the brown wire and splice/solder to the heated seat pair of wires (match the colors!) on the new seat. The other plug (two red and white wires) needs to be looped to itself. I opted to keep the pigtail but you can also cut it from the harness side and splice/solder the ends together that way as well. The seat heaters on the 987/997 seat appears to be by controlled by the two wires only. That’s all you need to do for the heated seat.






For the seat back, simply splice/solder the other pair of red and brown wires to the seat. Ziptie the relay to the bottom of the seat. Just make sure it is somewhere that won’t interfere with the seat tracks. If you haven’t already, install the 996 seat belt latch to the seat and run the wire to the bottom of the seat.




Before you put the seat in the car, I recommend putting a towel or something over your console and be careful around your door sills. Have the tracks fairly centered and fold the seat back forward. I found it easiest to tip the seat sideways to install it. It is tricky because of its height and you will probably get frustrated, but it will go in with some patience. Before you bolt it down, plug everything in and verify that the seat backs work (you can do this without turning the key). Also check to see if the heated seat is working. If the light doesn’t come on or only flashes on, then verify your work. If it works, bolt it down and time for the driver’s seat!



The driver’s seat is a little more complicated because of the memory seat function. There is an ECU under the seat that as far as I can tell, you need to keep. Even your wing mirrors run through this ECU. Although the 996 seat is very different, the 987/997 seat wiring is identical both sides. So again, label the appropriate wires and cut as before. On the 996 seat, the heated seat wiring harness is the same as the passenger side so repeat all of the same steps as before.




Next, remove the ECU from the seat. It is held in by two screws. Now, before you get overwhelmed by all of the wires, I am including the diagrams I found online and you can also take comfort in knowing that about half of these wires are not used and can be removed. The plugs are all labeled on the ECU, in German, but with the diagram is pretty straight forward. The only ones you need to keep are the long, white connector, the blue and black one in the middle, and you’ll be raiding two of them from the lumbar (Lordose) plugs. This part took some thinking and figuring out because the wiring for this ECU is frankly weird and didn’t make a whole lot of sense, even after I figured out a way to make this work and to be honest, I’m not sure why this way worked but it did! Take any two of the remaining pigtails, I picked two that had big white wires on matching pins, and cut the wires. Leave the white wires long and cut the rest short or remove them from the pigtails. On the ECU they will plug into slots 9 and 10 pins 1. This is where I am a bit fuzzy on which one was which, but I believe the red wire from the seat goes to slot 9 pin 1 while the ground (brown) wire goes to slot 10 pin 1. Once spliced/soldered, plug everything into the car and test to see if it works. If the seat back buttons are switched, then switch the pigtails in slots 9 and 10 around. Bolt down and you’re done!







Now you can enjoy lighter, more bolstered seats! I’ve been driving around with them installed for about a month now and these seats hold me in place around corners so much better than the old ones. I also don’t feel like they are any less comfortable. I have not done any long drives (nothing over an hour) in the car yet but I love them! I am 6’3 and don’t have the seat all the way back and I even had to raise the height adjustment up a little bit to feel like I sit about right in the car.




**This post will be edited for inaccuracies as needed**

hatchetf15

Great write-up Chance! I’ve been toying with getting some 2-way 997 sports for my car. Knowing which red and brown wires are which is huge! My wife is already rolling her eyes....great.

barbancourt

In summary... buy 996 sport seats instead.

Chance Hales

Thanks! Figuring out which wire goes where was the hard part. I had to redo the passenger side heated seat stuff because I didn't think the relay was needed.

When deals are found... This swap isn't nearly as bad as it sounds and the seats fit nicely and the pattern is better imo. But even so, 996 sport seats would be easier to swap but you's still have to figure out the wiring for the drier's seat because of the ECU.

c didy

Nice work! So no airbag light and problems if you use the 996 latches/ receivers?

Chance Hales

Correct, no issues with the light.

vitaminC

So when will you be selling a wiring kit?

Nice work and write-up!

808Bill

Subscribed.
Thanks for taking the time to document this Chance!
I got a great deal on some Cayman seats that where removed when new for a track car. Can't wait till they arrive!

Chance Hales

If only that proved profitable! I don't imagine there'd be a lot of demand for it to be honest.

Thanks! You'll love them! I just did my first canyon run since installing them and these are a night and day improvement.

dporto

^^^ Nahhhhh... The 997 seats are much nicer

Subourbonite

Also, the swap is not that difficult if you are going to sliding 997/Cayman seats with only power recline. Only things that need to be addressed are seat power and seat belt connections.

If you swap over your 996 belt receivers that's only two wires per seat. Now, that gets you power recline sliding seats, not heated 18-ways, but yeah 997 sport seats are light years beyond the 996 seats.

All the parts are available to make a jumper harness and avoid any splices. Mine are in and using 996 belt receivers for now. Jumper harnesses should be done in another week or so as soon as I get time. Write up and P/Ns coming soon.

Chance Hales

Agreed! Better quality leather, nicer design as far as trim is concerned too.

Yeah, it's really not that difficult. You just need to know which wires you need and don't need.

Tom2769

Sub, did you finish your jumper harnesses for this project? I'm considering a 997 seat swap and would be interested in info on your harnesses if you've already invented that wheel...

Chance Hales

Didn't realize I never responded to this. I just reused my old wiring and cut and soldered as shown above.

Tom2769

Yeah, I just finished this project on my C2 and did the same. Your original post on this was a good resource - thanks.