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Discussion Starter #1 (Edited)
This is a pretty big project.

I used E46 lumbar support [drivers side only] because it has two air bladders as opposed to the single E36 bladder, which suits my back better.

I used the latest carbon fibre heat pads and E39 switches, which are continuously variable.

The wiring was a lot of work as it was all custom, and I had to go through the firewall to get a high power supply.

I used the following parts
Fan connector parts:
61131387150 Fan connector, 17 way cuttable $2.22
61131393737 Fan housing cover 3 pol 3 61131393718 £0.08 61131393737 £0.29
61131393721 fan housing 5 way
Flat contact, fan connector 0,35-0,5 MM² ? 61131387140 $0.35
Flat contact, fan connector 0,75-1,0 MM² ? 61131387142 $0.28
Flat contact, fan connector 1,5-2,5 MM² ? 61131387144 $0.28
Flat contact, fan connector 4,0-6,0 MM² ? 61131387146 $0.43
61131389114 Relay base black $5
61131389113 Relay base black/white $5
61131389114 Fuse housing $2.22? £6
61138373666 6 pin housing (seat heat switch)
61136954554/61136931929 3 pin housing (Lumbar power)
Used lumbar switch, pump, bladders and harness (eBay)
W.E.T Automotive CF seat mats

Non BMW parts
Farnell 1330225 MQS female pin
Farnell 1328868 male pin for MQS
Loads of coloured wires
A fuse board
Some PC power connectors (9A pin rating, proven design, cheap and replenishable supply)
Fabric tape wrap
3 relays
Some sound dampening foam

First I fitted the seat pads and lumbar. There are DIY's for removing the seats and seat backs. You unbolt the seats, pry off the handles and remove the backs, unclip all the leather and the seat foams come away with the leather.

Cut all the hogrings

I wanted to cut the metal ribs that are in teh seat leather and slide them out, releasing all the hogrings in one go, like a magic trick, and then slide it back in afterwards. I snapped my cutters trying to cut this.

I considered these cheap Chinese CF mats.

They don't actually heat any part of the seat that your body touches no matter which way they were arranged they were too narrow or too short, so I bought some larger ones from a really nice eBay seller called bmwe46driver

These mats are a much better size. the bolsters are heated.

Insulate any exposed CF. There is a 23R resistance to any point in the mat [total resistance 2-3Ohms per mat], but you don't really want 500mA flowing in the seat bases making heat in the foam and coldspots on the mat. I checked the impedance all along, no hogrings touched exposed CF.

You can see the hexagonal grid arrangement of th CF that means no part of the seat gets disconnected. Don't cut the red feed stitches or the thermistor wires, they come pretty close to some hogrings.

You can see the NTC thermistor and the red supply lines that go around the perimiter of the seat pad in this picture.

I took the oppertunity to do some repairs to the seat foam and leather. I cut up a car wash sponge to fit in the torn driver's bolster, held in with webbed duct tape, and spray glued a chunk of chamois leather onto the back of the leather bolster where the fabric was torn.

This should increase the longevity of the seats in those high wear areas.

Re-hogring the seats. This took days and a lot of swearing. Not something I'd want to do again. Hogring pliers are a must.

Try and get needle tipped types that allow you to get into very tight spots. The ends had been ground off this borrowed pair by the owner, making them a bit more cumbersome.

I changed out the BMW power connector for the base heater for a PC one. The BMW MQS connector has no mating half/locking mech available from BMW, it is compatible only with the seat multiblock harness on E46/X5/E90 so it was useless.

The seat heat switches fit in the lumbar holes of the seat, with just the corners rounded and a little cutting below to suit the depth.

I had to dremel out a bit of the seat mechanism plastic, as the switch would not fit low enough. It neatly misses the seat height afdjust swing mechanism. The lever fulcrum now does twist a little in use, but when it is bolted to the seat it is not moving that much that I see it as a problem.

This bolt was a bugger to get at, and needs a long thin torx bit.

A regular BMW switch fits with no modification. Gotta love BMW :D

For the lumbar switch I had a bit of E38 trim that came with the switch, and used a hole saw on the fron of the seat.

I drew a cross from corner to corner; measured and made sure the body of the switch was both central and a little low in the facia or it wouldn't have fitted.

I used a hole saw for the hole and cleaned it with a dremel and some wet-n-dry.

Be brave! This part of the seat is not cheap to replace.

Here is the E38 trim. I wanted to use this instead of fixing the switch to the chair becuase it gave the a better looking mounting depth.

The switch protudes a fair way from the body, and I wanted the switch to be removable for replacements.

I cut it and ground down the face as thin as possible.

Fixed in with Araldite overnight.

Next I ziptied in the airbag bladder, It sits a little lower than you might expect, the markings on the grey fluffy part show that, and I have retrofitted lumber into an E46 and it is the same.

I tried it hanging from the next spring higher on the E46 - wasn't comfortable.

And rearranged and fitted the pump and valve. The pump motor is tucked in on the left, valve on the right. They are rock solid to avoid vibration noise.

This void is the OEM position for the lumbar guts, it sits on a plate fixed with one bolt dead centre. The plate is not available seperately.

This is what went in to the seat.

After a good clean with soap and water and reassembly the seats are done. Phew.

For the wiring harness, I have run a 30A cable into the fuse box and connected to the permenant live there. I'm using this for my Reinhold remote roof too, so there is a second relay for that (thread about that to follow when it's done).

I have a relay that comes on with the ignition, that feeds a fuse board of 8 fuses. I wanted this arrangement as each seat needs 10A for the mats, the lumbar needs another 2. There is a cigar ligher in the glovebox now that has a 10A fuse.

Running the wires through to the fusebox is a major PITA. BMW EBA say to undo the four screws holding in the engine bay fusebox to release the engine bundle cover. You must do this to release the cover (or you'll snap it), and there is one screw that you simply cannot get at (bottom left), the other three are 5-spanner awkward too. You'll be upside down in the footwell swearing all day at it.

You can see how hard it is to get to the engine bay fuse box fixings, let alone trying to put them back.

My suggestion is drop the glovebox, cut the ziptie at the fusebox (RHD car) and (carefully) poke a screwdriver through the outside area of the harness bundle. Wiggle it down till you see a crack of daylight and then thread through the one or two wires you need. Iv'e down this on my E36/7 and it worked well. You may get away with not removing too much from the area too. I also ran a couple of spare wires in case I need them in the future.

Can you see the glimmer of daylight here? Enough to get 1 wire through at a time.

After using a spare fan connector for permenant live and identifying the line I needed for the Reinhold, I was done in the engine bay area.

The power goes throguh an IGN activated relay, into the new fusebox and through 30A cables to the seats.

I picked up the illumination from the fan connactors. Ground is picked up at the grounding point next to the door to unload the wiring at the fan connecotrs from excessive current.

The PC connectors I used at the seats I chose becuase even though I have acess to all sorts of connectors at work, they are all a bit obscure and in the future if they need replacing then I can get these easily, and cheaply. I bought 8 kits, and BMW connectors can be £5-10 each. They are well proven, a half billion PCs sold worldwide can't be wrong :D. Each pin is rated at 9A, so I doubled up to give me 18A max at the seats for a 12A (driver's side) load.

The MQS connectors in the seat swtich at rated to 7.5A/80C so I unloaded it using a relay. One pad still gets heated by the switch (3Ohms load - 4A drain) to prevent the switch detecting a break in the heating elements and shutting off.

The relay is wrapped in foam to quieten it as the PID in the switch activates it quite a lot.

There is going to be SMD resistor in the switch in series with the NTC sensor to create an offset to the temperature and get the heat up to suit my butt.

The E38/E39 use LED illumination with PWM (E38) and a variable voltage (E39) (according to the WDS). When V_ILLUM is at max (10.2V) VF (LED) is 1.8V, dropping to about 1.3V when dimmed to 3V.

Sorry for the long winded thread.:embarrassed

2,493 Posts
Great thread Joylove! What model are they from? I've seen E36 seats with the lumbar support rocker switch at the side but I have never seen these!

1,500 Posts
Discussion Starter #4 (Edited)
Great thread Joylove! What model are they from? I've seen E36 seats with the lumbar support rocker switch at the side but I have never seen these!
The CF mats are from a modern BMW, E46 or E90 or something. The CF mats are better than the nichrome wrapped cotton found on E34/E36 for a few reasons.

1) They heat up a bit quicker than nichrome (need more juice though, hence the unloader relay under each seat)
2) Carbon Fibre is more flexible and it is multistranded and less likely to break when you sit on it than nichrome wrapped cotton.
3) Even if a CF link does break, the honeycomb pattern means you only lose 2 or 3 sides of 1 small hexagon, whereas on E36 one break means the whole mat goes dead.

Dead E36 mat with just two breaks in it.

CF mat with honeycomb pattern can tolerate breaks while continuing to work.

For the lumbar, it's a full kit from an E46, switch, harness and all.

That switch is used on all cars E46/E39/X5/E90/Z4/E38/X3 etc with lumbar. Only the E34 and E36 got the rocker switch arrangement (possibly pre facelift E38/E39 - not sure). I went that way as I retrofitted lumbar to my old E46 and found it more comfortable to have the bags at different pressures. On the E36 I need the bottom bag fully inflated and the upper one about 30 or 50% inflated.

Also on a long run I can change that balance in the bladders to reduce lower back pain from sitting in exactly the same chair for ages.
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