Hey everyone so I ordered some e38/e39 rear seat heater switches from a autowrecker on ebay for cheap and i just got them in! The great thing about these switches is all heating control is within these little switches and they have a great little wheel on the front to adjust heat, not just hard settings. I finally think I figured out the wiring after a lot of digging through BMW forums. I will confirm soon when I hook up it up in the cruiser. Still not sure where to place the switches, maybe something clean in the center console. I have a fantastic aux relay block from
@slcfj62 that I am already using for the power seats. There are some extra relays so the plan is to activate the relay with a ignition-hot 12v source, the run the hot relay wire to pin3 on the switch (wiring diagram says switch should get power from a power source with a 15amp fuse). Then from switch Pin 5 route the wire to Pin 25 under the seat. Pin 23 under the seat will connect to pin 2 on the switch to supply the negative thermal coefficient (NTC) signal. That signal is what I believe tells the switch when the seat is hot enough. Pin 1 on the switch connects to night illumination 12v source. I am not sure we need to connect Pin 6 to anything as the front seats heat both the seat bottom and seat back from pin 25. On the rear heated seats in an e38/e39 there seems to be an extra pin, hence the pin6 on these switches. Anyways, if I don't catch on fire due to poor wiring I will report back my success and confirm the wires are correct.
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