Heated Seats
by GSB | February 17, 2005 7:41 pm
After exchanging a couple of PM’s with Darth Paul, who has already fitted these some time ago, I had a crack at it myself… I think its safe to say its not nearly as straightforward as it looks, so if you intend doing it yourself, leave yourself plenty of time and make sure you have the right tools and materials. For reference, the job took me just under 3 hours from start to finish, so if your unfamiliar with cars in general, and with upholstery and electrics specifically, allow yourself an easy day to do it so theres no mistakes.
Also note that this is not a definitive set of instructions, merely a rough guide to the way I installed the seat heaters, and I can take no responsibility whatsoever if you choose to copy me and screw up your interior. Also note that the photos below show the custom leather interiors fitted to mine and DP’s cars, so there may be a few detail differences in leather seams, and fixing placement compared to the stock leather or cloth interiors. You’ll also note that both Paul and I have more or less exactly the same interiors, which is neither a sign of copying, plagiarism, or lack of originality. It’s merely a sign that we both have astoundingly good taste… 
So, those of you who have bought the kits via Stevewarbs GB with Tem’s contact with Toyota Finland will note that you have 4 rectanglar pads, a bunch of wires, and a couple of switches. So lets start by sorting out these bits and working out where they go. The pads come in pairs and have a couple of self adhesive strips to secure them inside the seat. You’ll also notice that the pads can be split by unplugging them from each other. When unplugged you’ll see that most of the wiring loom is left attached to one of the pads, this pad also contains the thermostat unit, which can be felt as a lump within the pad adjacent to where the wire joins to the pad. Dont worry, once its in place you wont be able to feel it.
The pad with the thermostat is fitted to the backrest, and the one with the shorter cables and the single plug at the end is fitted into the seat base. The location of the switches is entirely optional, but frankly the only obvious place is in the centre console, so thats where I put them.
Heres a rough guide to the location of the pads once installed:
So, grab yourself a ratchet and a 14mm socket, drop the roof and the windows, and whip the seats out. Not forgetting of course to unplug the electrical connections underneath… Oh, an d be very carful when pulling the seats out of the car, its very easy to scratch things.
Once out, you’ll need a sturdy workbench, and some clean rags or similar to rest the seat on at all the peculiar angles required for this job. I started with the drivers side seat:
Next, you’ll need a pair of sidecutters and small terminal screwdriver. remove the seatbelt sensor plug from the base of the seat, and cut the cable tie securing the wire to the springs. Next, you’ll need to remove the height adjusting knob from the side of the seat. This is secured by a spring that you can push off with your terminal screwdriver, the picture below will show you what your dealing with here:
Next, take a 12mm socket and a ratchet, and remove the four bolts that secure the lower seat squab to the subframe. Once these are removed, you should be able to lift the squab from the rest of the seat, leaving it looking like this:
The leather on the seat base is secured at the rear by a long black plastic strip, this will need to be unhooked from the steel seat base to allow you access to pull the cable through:
The arrangment at the front of the seat base is similar, but using a similar hooked over plastic strip that goes across the front and part way around each side. Once unhooked, the front of the leather cover can be lifted, exposing the foam underneath: (Err… Sorry about the messy workbench!)
Next take the pad that does not have the thermostat inside, and feed the cable through from the front to the rear of the seat, along the side that runs next to the centre console. Small hands are good here, as you’ll need to feel around for a way through, and pull the cable out from the rear of te seat squab. Once through, you can position the pad itself under the leather cover. The pad will end up in a postion where the cable entry is in the rear, with the adhesive strips against the foam base, like this:
Once in position, the pad will be up against the seam at the rear of the cavity (possibly just a custom leather thing) and the cables routed so you wont be able to feel them once the seat is back together. Once your confident that the pad is in the right placem remove the paper strips and stick the pad down to the foam:
Once its all together, refit the leather cover and hook everything back together underrneath. At the rear, make sure the cable emerges at the correct side before refixing the black plastic securing strip.
Next, we move onto the backrest. Place the bottom part of the seat squab to one side, and spin the main part of the seat over so its resting on the headrest and the front edge of the subframe. Heres where it gets interesting… The joint in the leather at the bottom of the backrest is “stitched” together using a legth of steel rod. This rod was bent over at both ends and is made of that really annoying material that is impossible to straighten… So, out with the bolt croppers to chop the end off, leaving plenty left over to thread it back in of course…
Once pulled out, the cavity for the heater pad is easiily accesible, so insert the pad as before, and stick it down to the foam. Now it gets ugly, threading the rod back in will be alot easier if you have a file or a grinder nearby to round of the end and stop it snagging as you push it though, and a damn site easier if you have an assistant with you. Of course, with persistance and a bit of time its do-able on your own. Once again, make sure the cable comes out of the correct side before re-assmbly.:
Once the 2 pads are in, then reassamble the seat, and connect the 2 pad cables together. Use cable ties to resucure the seatbelt sensor cable and the new heater cables to the springs, and dont forget to put the height adjuster knob back on.
Repeat the operation with the passenger seat… 
Next, the switches and the wiring….
Unscrew the gearknob and the four cross-headed screws in the sides of the centre console. Lif the console up and turn it over and you’ll be able to unplug the window switches and remove the console from the vehicle. Once out, apply a piece of masking tape, and then measure and mark up where you want the switches. Drill a small pilot hole, and then run a 20mm hole saw through the console at the 2 switch positions. The switches will then snap straight into the holes:
Now the wiring. Its pretty simple really, you need a 12 volt feed wire to the switches, and obviously you’ll need a negative earth wire as well. The red cables on the pads need to connect to the centre terminal of the switch, and the black wires can be joined together and routed to earth for simplicity, or if you want the little red lights in the switches to work as well, you can wire the switches as shown below:
In the photo above, the red and grey wires heading off to the left are the main power feed, which will be connected to the power source in the car. The red positive wire goes to the + terminal of each switch while the grey wire is connected to the gold earth terminal of both switches (this connection makes the little red lights work) as well as to the negative return wires of both seat heaters. The centre terminals of the switches are in turn connected to the red wires of the seat heaters… You can see the pairs of wires for each seat heater heading off to the right in the photo above.
Once its all wired up, put the console back in the car, not forgetting to reconnect the window switches. Feed the 2 wires for your power feed under the carpet in front of the gear shifter. If you split the carpet open behind the ashtray (theres a velcro strip that holds the 2 halves together) you’ll be able to feel for the cables and pull them through. Fully re-install the centre console leaving the 2 power feeds for your seats dropping out of the sides adjacent to the centre console cup holder. You can now install the seats, connecting your new power feeds to the seat heaters and not forgetting to plug the seatbelt sensors back in before bolting it all down. Dont forget to leave enough slack to allow the seats to move back and forth.
Once everything is together, you can connect the power supply. I used the cigar lighter supply, as its more than man enough for the job, is switched with the ignition system, thus eliminating flat batteries from leaving them switched on, and is very handily positioned. If you choose to use the same supply, then I think the pinky coloured cable on the back of the cigar lighter is the positive feed.
Thats it. Switch on and enjoy rosy cheeks!
Source URL: https://midshiprunabout.org/mk3/heated-seats/