DIY: Complete E36 Heated Seat Retrofit Step by Step

[boarder2k7]

If you don't want to break into the fuse box you can add an aux power block by the positive post and switch a fused line to the seats from an ignition switched relay.

[Seanmk2]

What if I don't mind getting into fuse block? What do I do then? This is much more intense than I thought.. Do I run wire to fuse locations 4 and 23? (Seat heater fuses) or can I just make my own harness?

[anerezcy]

With the seat pads removed from the seat frame you can get started on the upholstery. This is actually really easy, as long as you use the proper tools.

[brunp]

Love this thread, I am installing heated seats into my E36 325i which I am restoring. Used to be my dad's and the entire interior is gutted, so I figured, its the best time to retrofit for heated seats. :-)

Paul

[brunp]

Illumination Wire Connections

With the ground wires connected and the illumination wires put in place, you can now insert the relief relay into the relay socket on the retrofit harness. On the side of the socket is one set of guides with a locking tab. Slide these guides over the end position on the breakout box (the position that would be most toward the rear of the car when the breakout box is put back). After the relay is on, you can put the breakout box back in its original place.

This finishes up the wiring connections. Now you just have to route the seat heater switch connections and the connections for the seat heaters themselves.

Routing Wires:

I found that the carpet was much too stiff to lift up and really effectively route the wires, so I just tucked my wires down along the side and there were not sharp edges and I felt good about that.

To get the carpet free up you need to remove the side trim. The snaps are pictured in one of the photos below. Just pull straight up with a quick but firm/strong jerk and you'll pop one or two of the snaps and the rest come easy after that. Pull straight and not too close to an end or you will crack the trim. I did that by accident on one, but was able to repair it easily with some super glue and the crack is invisble.

With the side trim off you can push the carpet away from the frame and route the wire down in the crevice about 4 inches or so. Then lift up on the carpet a bit and you can route the connectors underneath the carpet and over the 6 inches from the edge to the cutout where the other seat connectors come up. Once you accomplish that, tuck any excess wire back down, and snap the side trim back on.


Center routing
Before you proceed you'll need to remove the passenger side under dash covering. There are just two screws and this pulls out. Then you can remove the passenger side trim and the passenger side speaker cover.

Next, you can route the passenger side connectors and the heated seat switch connectors. I routed them up along the main harness and over hte steering wheel. I zip tied about every 6 inches to make sure it wouldn't get caught on anything. There should be a smaller wire harness that breaks away from the main harness over the column and passes down between a couple of aluminum tubes for the AC system right along side the center stack. Run the heated switches down along this harness and ziptieing as necessary (after you've completed the run of course). You should be able to fish the connectors through to where the cigarette lighter is. Pop off the shift boot (pinch the sides in toward the center and then pull up and it'll come right out). Then pull up the foam sound deading material. You should be able to get your hand in by the cigarette lighter base. Just push up to pop out the blank covers for where you want to put the switches. I also popped up the AST switch to give myself more room. I felt around until I could find where I had fished the retrofit harness connectors to and then pulled them through as you see in the picture. Don't connect the switches yet though, as you'll need to figure out which is the passenger side and driver side in a little bit.

What is the part number for the relay above? I scanned this entire thread, but couldn't find a specific part number? It is the light green relief relay that connects into the harness?

[brunp]

Hello! I have question to Turfburn. Why did you insert green/blue wire to blue/green fan connector ? Thank you

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Just use orange 4pin relay or light green 4pin relay

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Just use orange 4pin relay or light green 4pin relay

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ecs tuning still have the harness for sale. I just got mine from them week ago

Would this be correct?

https://www.amazon.ca/BMW-Light-8373...7907539&sr=8-2

Paul

[cms90158]

Anyway to see the attached pictures? The write-up is detailed, but some things are clearly explained with pictures. Thanks

[onesikM]

These threads from over a decade about without pictures are a real shame. I can’t seem to find why my driver seat at the ends of the harness just before the connection point into the heating pads aren’t supplying 12v power like the passenger side gets when I turn on the heated seats. Both high and low function nomrally on the passenger seat. I always assumed the driver seat pads themselves were broken overtime with people kneeling on the cushions reaching for things in the car, which could still be a problem we have yet to determine. As of now I can say for sure that I don’t see any power coming across the wires.

I was going to jump some leads from the passenger harness over to the driver side elements just to confirm the heater portion inside the seats do work before I proceed any further with this. I’ve swapped switche/relays and tried new switches but nothing differnt happens. I think there is a break in the harness under the carpet somewhere after the driver switch reaching the seat but where hmmm annoying e36 only problems.


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