Fitting a heated seat kit

Why and what you need

The author used his car every day through winter and disliked how the thin seats take the heat out of you on a frosty morning. He bought a Waeco kit on eBay for just over £60 (the maker also sells direct). He said the pad sizes were a perfect fit for the standard seats, the instructions were limited but had the important circuit details, and they also add a little padding. In 2020 someone asked for a recommended kit, since there are many on eBay and the ones in the thread were no longer available, but nobody had answered when we collected the thread.

Part 1: the seats (about an hour each)

1. Take the hard top or soft top off so the seats come out, then remove the seat. The driver's seat has two hex bolts at the back and two cap heads at the front; slide the seat to reach them. See Seat removal.
2. Lift the seat out and put it beside the car to take the seatbelt off (a 17 mm socket, as he remembers).
3. Pull the leather away from the back of the seat. It is held with glue and comes away fairly easily. Peel the leather folded under the front of the base back carefully.
4. Gradually release the foam from the base, trying to keep it in one piece, and scrape away enough material for the back pad. Vacuum the dust and clean the leather while it is off.
5. Fit the pad between the foam and the leather, working from one side with the other left stuck down. He used the square pad on the backrest and the longer pad on the base, because it suited the seat profile better, and put the base pad on top of the foam: under the foam, he said, would take ages to get the heat through to you.
6. Secure the backrest pad with the double-sided tape from the kit (keep some for all four pads). He ran the cables to the bottom and out at the front rather than making a hole in the plastic behind. Run the base pad cable to the front so it can wrap under.
7. Glue it back with impact adhesive (he spooned it on, and said it dries and rolls off if you make a mess, and that spray glue might be better for big surfaces). Pull the leather tight and under the front, make sure the contoured foam is seated correctly and the cables are where you want them. Gaffer tape holds the side while it dries.
8. Tidy the cables with tape, then sit the seat on the floor and sit in it to press everything together.
9. Repeat on the passenger seat. You may need to cut down an Allen key to reach the passenger seat's front cap-head screw.

Part 2: routing the wiring

1. Remove the gear knob (he needed a strap wrench) and the handbrake handle (two 2.5 mm grub screws), then take out the centre console by its two plastic screws.
2. The aim is to send the seat harnesses along the centre following the engine harness, up into the dash through the rubber grommet above the passenger footwell. Take the dash plates off, undo the three screws (some models have an extra one behind the name plate), disconnect the battery negative, lift the dash and disconnect the starter button switch before you snap its wire. The dash pivots on two studs at the front, so push it up, pull the instrument binnacle towards you so its clip comes free, then lift and rotate it out. Tricky, he says. See Dash top removal.
3. Cut the ready-made harness at the switches so you can pass each end through. The wires are labelled, so keep the switches safe. Poking the wires through the tight grommet took persistence; a bent wire helps.
4. Refit the seats and connect the seat connectors as you do. Cable-tie the harness once both seats are in, leaving enough slack for the driver's seat to slide.
5. Keep the wires away from the gear cables. He first ran the cables down inside the handbrake area near the gear cables, and they interfered with second gear and caused nasty noises. They now run down the sides of the console to the floor. Check the gear lever movement before you refit the console.
6. Bring the other end of the harness (with the relay and fuses) from the battery compartment into the dash. He found the grommet too tight, so he drilled a hole behind the wiper motor cover, fed the wires through, then fitted a grommet and sealed it with silicone.

Part 3: connecting the relay

There is a circuit diagram in the kit instructions. This is how one owner wired it, so check it against your kit:

• Switched feed (to the relay's orange wire, pin 15): he tapped the thick green wire for the interior fan, which goes to the 20 amp fuse number 3 in the owner's manual. It was hard to find without removing the fuse box, so he moved harness wrap and checked continuity with a meter. He used a scotch block, covered in tape and kept dry, to avoid cutting into the car's loom. Another owner took the switched feed from the back of his stereo connector (check with a meter for the pin that is only live with the ignition on) and used a scotch lock.
• Heavy feed (red wire, pin 30): to the battery positive terminal. He made extensions with suitable wire and large ring terminals, soldered with heat-shrink, and protected them with air hose. A follow-up owner said he fed the heavy current directly from the battery, because piggybacking another live feed could overload that circuit. A 2016 reader asked whether the cigarette lighter feed would do: the reply was that it can't take much current, as it is a very small gauge.
• Earth (black wire, pin 31): the first owner bolted his to the plate that holds the battery. A later owner found that the alarm unit's fixing bolts were no good as an earth and moved it to a bolt in the middle of the dash, thinking it was an airbag unit. Don't use a safety system bolt for this: use a proper earth point. Another reply said the earth is better bolted down than held on a screw.
• Fit the relay on the studs shown, keep the harness bulk under the wiper motor cover, and re-link the harness in the dash with the battery disconnected and the ignition off. He soldered the wires he had cut and finished with heat-shrink and spiral wrap.
• Refit the dash. A tip: push each screw through a piece of tape and tape it to the screwdriver, or you will keep dropping them into the dash.
• Switches: he drilled two 20 mm holes in the dash plate with a stepped hole cutter and said to spend a lot of time getting them right. They are in that position because there is a gap in the aluminium. Another owner put his on the centre cup holder. One owner who rushed the holes got a rough edge.

What went wrong for others

• Illumination: one owner wished for illuminated switches, because both pads on maximum draw about as much as the headlights. The supplier only had the handbook diagram. Later kits had LED switches, but one owner found the LEDs lit whatever the switch position, so he dotted them out with a marker. Another added indicator lights near the switches so he wouldn't forget the passenger side.
• Not working at first: one owner who didn't know electrics got it wrong the first time. The stereo signal wire wasn't making contact and the earth was poor. He found both with a meter and a bit of thinking.
• Gear noise from wires near the gear cables: covered above.

While the dash is off

One owner who fitted the seats used the opportunity to improve the heater: he replaced the thin foam piece linking the heater duct to the dash, removed his earlier sock filter mod, lagged about 18 inches of the hot pipe on the driver's side and checked the dash for air leaks. He said the biggest improvement came from beefing up the rectangular coupling between the heater vent and the dash, so less hot air bled into the area under the dash, and the heater became much better for demisting. The first author had resealed the heater box and dash earlier and fitted a heated screen. See T7 Design replacement heater for an alternative heater.