seat retrofit issue

[lionkingns]

So before NY bought a pair of e38 16way comfort seats in solid condition for a nice price, finally got all the cabling done yesterday, the motors and buttons work, but I cant get the heating to work, the buttons on the center console do nothing, all the cabling is checked like a dozen times. The resistance in the heating circuit on the seat is around 1.5 MegaOhm, which is a bit high in my opinion , I have tried giving direct 12v to the heating pin, no luck. Also I pulled of the back, and checked, looks like the back heat plug isnt connected at all which leads me to think there are no heaters at all . So is there such a thing as a electric comfort seat without heating with prewired loom and how to make sure ? And if not how to check the heating elements

[Jaaap]

These seat heaters regularly stop working after 15+ years, cause is some break in the electrical wiring in the pads.
15 MΩ is way too much, should be 3Ω or so.

[BimmrMeUpSnotty]

The E38 and E39 wiring for the heat is different, I think. I had also gotten the 16 way E38 comfort seats, 2001 E38, placed them in my 2000 E39 528 wagon, same thing, heat didn’t work, original seats heat worked. I never bothered to find the correct way to fix them, never bothered. But I believe they have to be re-pinned to the proper receptacles in the E39 harness. So compare the harnesses, see what is different, trace the wires, just to be sure they are going to the heating elements, then they should work. Come back on here and let us know what you find.

[MotorMouth93]

1.5 megaohms is effectively an open circuit. Sounds like something is broken.

[TiagE39]

@lionkingns, the yellow connector E38/E39 comfort seats were all pre-wired for seat heating (they just used one universal harness with connectors for all possible features), but do not always have the actual heating pads installed. Therefore presence of the white/yellow and white/blue seat heating wires isn't positive proof of seat heating. An easy way to check is to go to the back of the seat and inspect where the seat bottom leather fastens into the rear bottom seat frame. If heating is installed, you should find a black sheathed pair of wires emerging from the bottom leather folds and ending at a mauve-colored connector with the aforementioned white/yellow and white/blue wires. That's the cable for the bottom heating pad.

[lionkingns]

@TiagE39 the answer I was looking for, did a bit of wire tracing and found the heating plug at the back lower part that goes to nowhere so I guess I did get a pair without heating, will need to speak to the guy that sold them to me

[TiagE39]

@lionkingns - sorry to hear that! You can always add heating pads yourself but it will involve taking apart the seat and removing the leather skins. There are a lot of aftermarket cut-to-fit heating pads that can be used. Another option is sourcing heated leather from another comfort seat and installing that.

[Twistytee]

I did this project on my e36 seats with aftermarket carbon fiber heating elements. Although disassembly of the seats was not fun, the carbon pads don’t kink and burn out the way the OE copper wire pads do. And it was far cheaper than sourcing BMW heating elements. I used zip ties instead of hog rings to reattach the leather covers and felt the end product turned out well.

[BimmrMeUpSnotty]

Zip ties??? You didn’t do as I did? Order two bags of hog rings, the hog ring pliers, finally tackle the job, finding out what a pain in the butt it was, just to pull the leather off, then decide that an upholsterer deserves what he earns and be done with it??? ZIP TIES??? !!!

[MotorMouth93]

I used zip ties instead of hog rings when I replaced the bottom seat foam in my car. Still looks perfect 20k miles later.

[BimmrMeUpSnotty]

Those zip ties are gonna snap at 20,999 miles.... Hope I’m wrong, hell, the way I eat Mexican food, those zip ties would not have lasted 1000 miles.

[lionkingns]

since I am a don't ask how it looks or how it works, as long as it works kind of guy, pulling apart something that should look pretty is a no no for me, so will be searching for a heated pair of seats

Since I did find one pair but in creme color, and I need black, any of you have some expirience with color changing the hole seat ? I know people do it, just not sure how long does it last ?

[TiagE39]

lionkingns: honestly disassembling the E39 comfort seats isn't hard, they're very modular and were clearly designed to be disassembled and serviced. What I find the most interesting is that the Standard, Sport, and Comfort seats all use the same bones and modularity, as if BMW intended someone with say a Standard seat to upgrade later to a Sport or Comfort. Especially true of the later yellow connector seats.

I just finished a project replacing the leather bottoms on a set of comfort seats and I have no previous experience in upholstery. If you're mechanically inclined in general and you have a space to take the seats apart, it's not impossible.

You can certainly re-dye the leather but in my view that's going to be a harder and more technical process. Aubergine on here and myself have done dye work to tan comfort seats a few times (I forget the name of the kit he used, maybe he can weigh in) and while the end results were very good, that was largely due having good practice (we honed our skills on a throaway seat first). That said, the scrubbing/sanding/filler/dye process does change the appearance of the leather and reduces the appearance of the grain significantly. If you don't know what you're doing you can remove a lot of detail in the leather and make it look very flat/artificial.

[Dash01]

[QUOTE=TiagE39;30624775]lionkingns: honestly disassembling the E39 comfort seats isn't hard, they're very modular and were clearly designed to be disassembled and serviced. What I find the most interesting is that the Standard, Sport, and Comfort seats all use the same bones and modularity, as if BMW intended someone with say a Standard seat to upgrade later to a Sport or Comfort. Especially true of the later yellow connector seats.


This also appears true for E36 seats, which have the same frame used for sport, comfort, and Vader (M cars) seats, so the pads are interchangeable.

In other words, if an E39 seat frame is to be upgraded to, say, an E38 comfort seat, just buy the E38 pads at PicknPull for about $10 each (as I recall) to plug & play into your E39 seat frames: So, no need to buy and drag home the whole E38 seats, or dispose of your old E39 seats.

I'm also told that 2 door coupe and vert seats are also interchangeable with the basic fold-down mechanism being the same as with non-fold sedan seats, just add the Bowden cable and side levers to a sedan seat to make it fold as a coupe/vert seat. This could be a handy feature in an E39 sedan with fold-down back seat capacity, or a Touring E39, if you wanted to make space for car camping with room to stretch out. (That said, I suspect that most E39 guys aren't particularly crazy about car camping, but for those who are, this might work.)

[BimmrMeUpSnotty]

I’ve camped in my wagons, fold the rear seats down and had an air mattress. Never even of the front seats those two days out at the flying field.

[lionkingns]

guys looking into some solutions, is there a way to make universal seat heaters work with the BMW central control unit ?

[TiagE39]

It's not impossible. The seat heating pads are just big resistors, and most universal cut-to-fit heating pads (https://www.amazon.com/KBD-Premium-Heater-Switch-Settings/dp/B08K4XLBTL/ref=asc_df_B08K4XLBTL/?tag=hyprod-20&linkCode=df0&hvadid=475825774283&hvpos=&hvnetw=g&hvrand=1121512874721038142&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9003545&hvtargid=pla-1111541855260&psc=1) will pull similar wattage to the stock ones. I imagine the controller wouldn't mind powering them. You'll need to use your own style of connectors to splice in, or source bad/broken pads to get the stock connectors from.

There is supposedly a BMW heated seat retrofit kit out there (with pads and connectors designed to work with the seat harness) but they're very hard to find and most likely NLA.

The most important thing is the seat bottom temperature sensor (white wire with blue stripe). This needs to be a ~10kohm NTC-type thermistor. Anything else and the controller will throw errors. You can get them widely on eBay for no more than a few dollars.

[lionkingns]

Great, thats nice to hear, I will buy the cut to fit heaters and thermistors and try it , will post the results

[Twistytee]

Interested to hear your findings. It worked when I did the e36 with the BMW controls, but they only have two settings for high and low and that’s what most universal heating elements come with. I did use a multimeter to make sure the resistance on the universal pads was within spec of the factory ones before stripping the seats and installing.

Since my e39 is not wired for heated seats and it’s a lot of work to retrofit a factory style harness and controls, if I ever decide to add them I think I will go with installing an aftermarket switch into the seat side trim and wiring to power with fuses to the rear distribution block near the battery.

[lionkingns]

@twistytee the issue is I bought a pair of electric comfort e38 seat being sure they where heated, did all the wiring and retrofiting of the central console and controls and all thw wires + I upgraded the older separeted controls to the newer one bar control module just to find out my seats did not have heaters in them at all, so after all the wiring I would love to have it working