Upgrading OEM European GT3 seats to heat using OEM components

Upgrading OEM European GT3 seats to heat using OEM components Disclaimer: The factory never made GT3 euro seats with heat, so we will be adapting std 996 seats components to work with the GT3 seats. Note: I have borrowed images, steps and lists from many sources to compile these instructions. These include the following people, Dennis Vogel, Pat Jeski and Carrera Mike from Rennlist, and of course Loren from Renntech. The only pictures here that are mine are the finished product… The rest are from them. Parts list excluding GT3 seats (note: If you do not have heated seats already, please refer to http://www.dennisvogel.com/heatedseats/index.html for instructions on how to wire up the switches and harness to adapt your car to heated seats and substitute these instructions when dealing with the actual seats. PARTS LIST PER SEAT - 996-618-531-00 HEATED SEAT RELAY (you can re-use your old ones but they do require disassembling part of your old seats to get at) - 996-612-540-01 SEAT WIRING HARNESS - 996-618-531-00 SEAT RELAY BRACKET - 999-650-180-40 ELEC CONNECTOR - 999-652-960-40 CONNECTOR COVER - 996-653-105-01 SEAT HEATING LOWER - 996-521-539-00 SEAT CUSHION UPPER - Iron on cloth patches from a department store (I recommend a tan colour to match if your really crazy about the factory look in places people won’t look). - A bag of small black wire tires - 16 gauge wire- 4 pieces aprox 36” each (I recommend black as a colour to for a more factory look) - You may also choose when ordering your GT3 seats to get a new set of seat belt receptacles, I did to make it easier so I minimized what needed to be removed and unplugged from the old seats. TOOLS NEEDED - ½ inch E-12 socket for seat removal/install (I used a craftsman 3/8 E12 with an adapter) - Socket wrench ½ inch and some extensions (easier to break the seat bolts free) - Torque wrench ½ inch (so that you can install the seats/belts correctly) - 17mm socket ½ inch for seatbelts. (6 point recommended so that you don’t damage the finish on the bolts) - Flat Head screwdriver to remove the trim on the front of the seat rails and cap on seatbelt to body. - Phillips head screwdriver (needed if you are re-using the relays from your seat to remove the old mount, also needed on pre-2002 cars to remove the machine screw on the trim at the front of the seat rails) - Torque screwdriver T-15 (I think, only if you have memory seats, this is used to remove the screws on memory module to drivers seat so you can unplug it from the car). - Thread lock blue (removable) for the seat bolts - Soldering Iron - Clothing Iron - Glue Gun - Continuity tester - Diagonal cutters for the wire ties - Scissors - Razor blade Step 1: Preparing the back/upper seat cushion The upper heated seat element will come attached to a foam cushion already. You will need to separate the foam from the heating element and discard the foam. To perform this use a hair dryer to heat up the glue holding them together and peel. I used a heat gun, but it was too powerful and caused the separation to not be clean and I had to mechanically remove a lot of left over foam with my fingernails. It wasn’t perfect, but was as clean as I could make it. The next step depends on your skills with a needle and thread… All the GT3 cushions are attached to the seat with Velcro and have a Velcro opening which allows you access to the cushion to add/remove padding. The issue is the back/upper heating cushion has a stitch running across the middle that prevents access to the top half of the cushion. What is needed is to open up the stitch to allow access to the whole foam padding and then to use 3m spray glue to attach the element to the foam pad. The stitch will need to be redone, only this time you will need to perform a hidden stitch because you cannot re-stitch into the same holes. This is the tricky part, so I personally didn’t bother and went to a local upholstery shop. For about $70 bucks, they did the whole thing including the spray glue for both back/upper cushions. In fact I kind of like the look of the hidden stitch better as the cushions are filled out more with the elements in. They did need to trim a little of the element where there wasn’t any wires running to follow the line of the cushion before gluing. No big, when you hold the elements up to the light you can see the wires and where not to cut. I also verified everything using a continuity tester both before and after I brought the elements and cushions into the upholstery shop. Step 2: Preparing the bottom seat cushions. The bottom element comes with a self sticking back. The element is split in 3 places to allot for the stitching on the bottom of the standard 996 seat cushion. You will need to cut the element at the split furthest from the cable that comes out of the element. Then using a razor blade carefully slice through the material to retrieve the element wire at each of the 3 corners. Pull about 1 ½ inches up so that you can solder a jumper wire between the 2 pieces of heater element. Don’t worry if you accidently cut it, just keep at it until you get a clean piece of wire. A trick is to hold it up to the light to see which way the wire runs to cut right next to the wire and pull the wire out. You can next hold the separated element piece that is no longer attached to the factory wire/plug up to the light. You will notice most of that piece does not have any wires running though it. Since it doesn’t have wires that area won’t be “heated”, so cut most of that un-wired section off about an inch from the wires that run through the element. Next you will need to perform soldering of the jumper wires between the elements so that they are electrically one piece again. You will need 2 pieces of about 36” of 16 gauge wire to connect the two halves together so that the cushion still functions as a single element with a gap in the middle and fit in the two bottom cushions of the GT3 seat. To perform this, solder one piece of the 16 gauge wire to each side and then use a piece of cut iron on patches (the kind that are used to patch knees on clothes) to protect and cover the splice. One piece on each of the 4 corners. I would also advise cutting some strips of the iron on patch and covering the other 2 splits on the elements to keep them from having any issues in the future. Verifiy all your elements are still electrically one piece using a continuity tester. Finally simply peel and stick the elements onto the back of the foam part of the cushions and shove them back into the cushion, with the factory plug/cable on the rear most cushion. Note the Velcro on the front bottom and back bottom cushions will each be pointed toward the back of the seat. Step 3: Attach the cushions. You can now re-attach the cushions to the GT3 seats, running the wire from the back/upper cushion down through the sub belt hole in the bottom of the seat. You can then attach both bottom cushions running the wires from the rearmost cushion along the sides under the rear bottom cushion to meet the front bottom cushion and run the main factory plug wire down and through the sub belt hole in the bottom of the seat.

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Step 4: Removing the old seats (repeat for each seat) NOTE: DO NOT PUT THE KEY IN THE CAR UNTIL THE SEATS ARE PLUGGED BACK IN OR EVEN PUT THE KEY IN THE IGNITION AS THIS WILL CAUSE AN AIRBAG WARNING LIGHT REQUIRING A DEALER VISIT OR A DURAMETRIC SYSTEM TO RESET!!!!!! THIS PROCEDURE IS THE SAME IF YOU HAVE POWER OR MANUAL SEATS, YOU STILL DO NOT NEED THE CAR KEY THE POWER SEAT MOTORS WORK WITHOUT THE KEY, SO KEEP IT FAR, FAR AWAY. Move the seat to its extreme back location. For pre-2002 cars, remove the machine screw from the plastic trim at the front of the seat rails. To remove the two plastic trim pieces, gently pull up on the tab with your flat head screwdriver and slide it off the rail. Be careful, the tab is gentle and will break off, you only need to lift the tab a little and slide the piece forward and away from the seat rail. Next using your E12 socket loosen and remove the front bolts. Be careful these are special bolts with non-standard thread so if you mess them up you will need to get new ones. I cleaned the threads with a rag upon removal and put them to the side. Next move the seat to its extreme front position. And remove the rear bolts with your E12 socket. COVER YOUR DOOR SILL AND CENTER CONSOLE EACH WITH A TOWEL TO PREVENT SCRATCHING, ALSO IF YOU ARE REMOVING THE DRIVERS SEAT, MOVE THE STEERING WHEEL IN TO GIVE YOU MAXIMUM ROOM. On a 996 there is a lot of room but on a boxster you may have to find a better position to access the cables. On a 996, Lean the seat back you may want to prop it up with a block of wood and start disconnecting cables. To do this you will need to disconnect the main seat harness, this has a slide pull which will push the plugs apart when you open it and push them in when you close it. Open the pull. If you have memory seats and are working on the driver’s side, you will need to use a torx screwdriver to remove the module and unplug the two cables from the car to the memory module. One requires the flat head screwdriver to pull up on the tab so that is comes strait up from the plug’s side, the other requires simply squeezing the tabs on the side. You can re-screw the module back in when you are done. Now it’s time to take the seat out of the car. First pull the handle to fold the seat down, next lift it carefully out of the car. Remember these seats are very heavy compared to the new GT3 seats, so don’t be surprised. In a boxster, you may want to have the roof down so you can simply lift the seat out of the car. If you are going to retrieve the heated seat relay from the old seat, place the seat down on its side (buttons down, seatbelt receptacle up). Slowly work the plugs out of the two white plastic clamps on the front bottom of the seat, then pry each one off, this will allow the rail and bottom frame to separate from the seat. You can then use a long Phillips screwdriver to remove the relay from inside. This is not an easy task to do without breaking something by separating the seat and frame too far. Be very careful !!!! I recommend buying new relays to make the only really frustrating part of the install go away. Step 5: Final assembly of the GT3 seats Note: there is a left and a right seat and a left and right seat belt receptacle. The attachment post is longer on the seat belt receptacle side. Using a 17mm socket wrench install the seat belt receptacle (felt side out) using the torque wrench and 38 lb/ft torque, be careful to make sure the spacer is lined up and tight and the washer is on the inside of the belt as the bolt has built in washer Don’t forget to center the receptacle in the middle of the seat belt hole as a guide for the angle of the receptacle placement. You can attach the cable to the clips in the bottom of the seat, mine used all 4 and then ran back to the middle. I used wire ties to keep the double backed wire neat. NOTE: If you are re-using the old seat belt receptacle you will need to remove the wiring and disassemble the main seat harness plug to remove seat belt receptacle from the old seat. Pushing the GT3 seats each on their backs to access the bottom you will now need to install/assemble the harness and heated seat relay/harness. First you will need to push the double brown wire and the single wire with banana plugs from the heated seat harness into the main seat harness plug. Pin 6 gets the double brown and pin 3 gets the striped single wire. You should be able to see the numbers on the harness. I also double checked it by looking at the old seat. Once these are pushed in they are hard to remove without a special tool, which is why I didn’t do the final assembly till the old seats were out so I could double check. Next slide the small plug part of the heated seat harness into the main receptacle with the little plastic piece that juts out towards the outside. The little plastic part of the plug is a spacer to make sure the seat belt receptacle plug is in the correct place when you slide it in next. After repeating this process for the seat belt plug, then use the small plastic electrical cover piece 999-652-960-40 piece to slide into the receptacle and prevent the seat belt plug and the heated seat plug from moving. Next heat up your glue gun. If you have a sub bar attached to your seat you can elect to tap and “screw” the relay mount to the sub bar out of the way. I didn’t so I used a glue gun to attach the relay mount towards the front of the seat bottom out of the way of everything since the seat does have a lot clearance in the front area. I also took the two plugs where you actually plug the seat elements in and unsnapped the plastic mounts that are included and using a pair of diagonal cutters removed a part of the tabs so that I could get a mostly flat surface to glue the plastic mounts to the seat bottoms which will hold the plugs in place and out of the way. I put them on an angle near the middle of the seat making sure they don’t interfere with the seat rails and that the cables reached from the heated seat harness and from the elements. Work the slider handle to make sure you don’t interfere, you may not be able to actually move the seat on the sliders but should be able to see if you are in the way of anything. Next plug in the elements, slide the main seat harness into its plastic mount that is already there on the seat from the factory and clean everything up with wire ties to make sure nothing will get snagged with the seat rails. Step 6: Install the seats (repeat for each one, remember the car key thing). Using the flat screwdriver, remove the plug that covers the seat belt mounting point between the car and seatbelt end. Next remove the 17mm bolt and the seatbelt. Then re-install the bolt and cover. The GT3 seats require you to thread the belt through the holes top and side of the seat. Also in factory style,the seat belt will now attach to the side of GT3 seat. This is the correct location according to the factory workshop manuals and some car pictures of factory installed seats I have seen. Gently place the seat in the car (remember those towels to prevent scratching just in case) Lean the seat back (if a 996) and line up the harness from the car to the connector on the seat. Make sure the release is pulled all the way out, you can feel a little snap when it is, this will make sure it is all lined up so that when you push the release back in it will connect and lock the car harness and the seat. If you have the memory seats, you will need to wire tie of the two cables for the memory module that are attached to the car harness on the driver’s side out of the way. I attached them to car body and the cables for the computer under the seat. Move the seat strait up and thread the seat belt through the top outer hole in the seat. Make sure it’s strait, you can always flip the buckle around with a little bit of belt twisting, untwisting the belt itself would require removing the seats if you don’t get it right. Using a block of wood so that you can lift the seat up for clearance, proceed to thread the bottom half of the seat belt end through the seat belt hole on the outer side of the seat. And attach to the seat using the bolt on the side right near the seat belt hole. Be careful to make sure the spacer is lined up and tight and the washer is on the inside of the belt as the bolt has built in washer. Use 38 lb/ft of torque and the 17mm socket. Move the seat into a normal position and line up the holes. Start with the back bolts and use a little Thread Lock blue do not tighten all the way yet. Slide the seat all the way back and install the front bolts and tighten them to 48 lb/ft of torque. Next slide the seat towards the front and tighten the back bolts to 48 lb/ft of torque. Slide the seat back and replace the plastic trim on the rails. Pre-2002 will require reinstallation of a machine screw using the Phillips head screwdriver. Make sure both seats are installed and plugged in before you put the key in the car to test them out…. Remember the air bag light issue if you don’t have both seats plugged in. AND THAT’S IT, ENJOY YOUR NEWLY HEATED GT3 SEATS….

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wow... that's serious stuff right there. Good work! Thanks for sharing!

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Nice work!!! I used Dennis Vogel's instruction to add heat to my Comfort Seats 3 years ago, but you were really creative in adapting the OEM elements to the sport seats.

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Kind of one of the reasons I was staying away from GT3 seats, cold *** in the winter. Now you've ruined that excuse I'll HAVE to go out and buy some now, damn you! (great post!)

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Same reason I was ignoring them... and then Google got in the way and I saw it was possible, someone had done it before but didn't have very detailed instructions, which is why I made sure I did a lot of research and docuemented it when I was done. Now I have them, I love them and the heated part is way better than std seats because you are really held into the buckets and they do loosen up your back very nicely from the heat.

Quotes source post: 4412418

Quote: Thank you for the free bump!! Still offering great package discounts, PM to make a deal!

GT3 seats are my next mod just waiting for the rightr pair at the right price.

Hi...mine is an 09 coupe...same problem every once in awhile...generally if due to hard driving in 3 cycles light goes out...if you read with obd ii reader a lazy sensor. With number showing which one is acting up... if you clear using reader and bad sensor in 3 cycles it returns...then cheap fix to replace ....common If lucky just your gas cap loose and light goes out after 3 drive cycles too... ​​​​​​Good luck...

pretty cool stuff. too bad i don't really fit in the gt3 seats

Nice Work!

This was a awesome write up! Does anyone know if there are any pics anywhere that can go along with this?