Swapping Looms Pre-facelift to Facelift

[Z3_Irish]

Hoping someone can help here. I have purchased a set of leather pre-facelift seats so they have the 3 separate plugs instead of my current facelift seats which have the big yellow plug.

I have read a couple of guides and I believe I have a few options but wondering which would be the easier:

- Remove the seats totally from the bases and swap over - Seen this may be tricky
- Cut the loom connector off car loom and also the 3 off the seats and then splice together - Would mean altering the car loom which I ma not keen on
- Cut the loom connector off my current seats and and the 3 connectors off the new seats and fit my yellow connector to the new seats and straight connection fit then - Would seem the easier option if the wires are colour coordinated

Any help appreciated

 

[Nodzed]

You can buy adapters from BMW to covert one plug to the other

 

[Z3_Irish]

You can buy adapters from BMW to covert one plug to the other

I did see that but looking they seem to be over £50 for one unless I am looking in the wrong place so my cheap seat purchase would not be cheap so more paying £100 for looms. I thought the advantage I have is the seats I am removing are worthless really so would not be bothered chopping the yellow loom off I need as long as it is easy enough to match the cables as in they are colour coded?

 

[GazHyde]

You can chop the existing looms up and wire them directly if you want, been done many times before. Depending on your wiring skills you do risk introducing faults later on, but if your confident no reason not to.

 

[Z3_Irish]

You can chop the existing looms up and wire them directly if you want, been done many times before. Depending on your wiring skills you do risk introducing faults later on, but if your confident no reason not to.

Cheers so my preference would probably be to chop the yellow connectors off my current seats leaving some excess wire from the back of them. Then chop the 3 plugs off the new seats and connect those wires to the wires on the yellow plug and then straight connection into the car loom. I am pretty used to splicing cable together etc so not worried about that.

My worry is are the wires colour coordinated and match between pre-facelift and facelift so it is a simple case of match the colours and joining

 

[GazHyde]

There are various electrical manuals in the articles section which may help. Various years are available...

https://zroadster.org/resources/

For example the 1999 version https://zroadster.org/resources/1999-z3-z3m-electrical-troubleshooting-manual.13/

 

[Sean d]

Cheers so my preference would probably be to chop the yellow connectors off my current seats leaving some excess wire from the back of them. Then chop the 3 plugs off the new seats and connect those wires to the wires on the yellow plug and then straight connection into the car loom. I am pretty used to splicing cable together etc so not worried about that.

My worry is are the wires colour coordinated and match between pre-facelift and facelift so it is a simple case of match the colours and joining

No they are not the same colour from seat to car, I was going to take this route but decided to buy the harnesses, I do have a couple of the yellow multi plugs somewhere.

 

[Z3_Irish]

No they are not the same colour from seat to car, I was going to take this route but decided to buy the harnesses, I do have a couple of the yellow multi plugs somewhere.

What I meant was are the seat looms the same colour coded between pre-facelift and facelift as all I would be doing it swapping the yellow plugs from my current seats onto the new seats in place of the 3 connectors?

 

[Sean d]

What I meant was are the seat looms the same colour coded between pre-facelift and facelift as all I would be doing it swapping the yellow plugs from my current seats onto the new seats in place of the 3 connectors?

No they are not, some of them are but not all, thats why I bottled it and bought the harnesses for £30 each

 

[Z3_Irish]

No they are not, some of them are but not all, thats why I bottled it and bought the harnesses for £30 each

Damn, it is never easy, at least got the leather door cards on which are nice. Don't suppose you have a link to where you got the looms as cheapest I can see are £52 each

 

[t-tony]

No they are not, some of them are but not all, thats why I bottled it and bought the harnesses for £30 each

Money well spent too Sean. It eliminates the risk involved.

Tony.

 

[Sean d]

Damn, it is never easy, at least got the leather door cards on which are nice. Don't suppose you have a link to where you got the looms as cheapest I can see are £52 each

Trade discount

 

[Lazzzydog]

I would have thought that if your current bases are in good nick then swapping the "new" seats onto your existing bases would be the easy option. That's the way I did it and it only took about half an hour each side. Nothing tricky about it at all. There are a couple of cables which operate the seat back to release and then re- attach but they are straight forward and there is no cost involved.

 

[Z3_Irish]

I would have thought that if your current bases are in good nick then swapping the "new" seats onto your existing bases would be the easy option. That's the way I did it and it only took about half an hour each side. Nothing tricky about it at all. There are a couple of cables which operate the seat back to release and then re- attach but they are straight forward and there is no cost involved.

Cheers I did have this as an option but I read this was actually quite hard to do. Do you know of a guide anywhere as this would be the easy option. I presume I would need to take the base off with the runners on and the plastic bit above it which has the switches and so forth on so that it is literally just the 2 piece of seat left?

 

[Lazzzydog]

Choose a dry day and drop the roof. The seats are held in by 2 bolts at the rear and 2 nuts on fixed bolts at the front, I think all are 16mm socket. Once undone tilt the seat upwards and into the car to gain access to the plugs to undo them.The one important thing that I cannot remember is how to leave the seats on there runners before removing from the car. I think it is have the seats all the way forwards but I will have to check tomorrow and let you know. They have to be in the right position to get access to the 2 screws that hold seat and base together.
Once the seats are out support them upside down on a work bench or similar to reveal the underside. Remove the screws holding on the plastic trims that conceal the lever and switches as these stay with the bases. The cables from the lever are like bicycle brake cables with a nipple at the seat end, one each side of the seat base. Free each nipple by slightly bending the tag on the seat base. The seats are held on to the bases by 2 screws at the rear and once these are removed simply ease the seats forward to free the 2 hooks that hold the front and the base will lift off the seat. Reverse the procedure to refit. I may have some photos somewhere.
If you are not too far away I would be happy to help.

 

[Z3_Irish]

Choose a dry day and drop the roof. The seats are held in by 2 bolts at the rear and 2 nuts on fixed bolts at the front, I think all are 16mm socket. Once undone tilt the seat upwards and into the car to gain access to the plugs to undo them.The one important thing that I cannot remember is how to leave the seats on there runners before removing from the car. I think it is have the seats all the way forwards but I will have to check tomorrow and let you know. They have to be in the right position to get access to the 2 screws that hold seat and base together.
Once the seats are out support them upside down on a work bench or similar to reveal the underside. Remove the screws holding on the plastic trims that conceal the lever and switches as these stay with the bases. The cables from the lever are like bicycle brake cables with a nipple at the seat end, one each side of the seat base. Free each nipple by slightly bending the tag on the seat base. The seats are held on to the bases by 2 screws at the rear and once these are removed simply ease the seats forward to free the 2 hooks that hold the front and the base will lift off the seat. Reverse the procedure to refit. I may have some photos somewhere.
If you are not too far away I would be happy to help.

Cheers for this, removing the seats from the car I have done and is quite easy as had to clean the current seats as were terrible.

Your guide on removing the base seem more straight forward so I am going to have a go at doing that on the new seats tonight so I can see how long it will roughly take before I remove my existing seats. Then may remove the passenger seats and have a go on that as if hit trouble I still have my drivers seat in to sit in when drive the car ha.

If you have photos that would be great and hopefully can do it myself but if not a helping had would be great

 

[Mac_Gaz]

I have exactly the same problem. Old seats, old connectors into a newer car.

The loom adapters from BMW are for the other way around (newer connectors on seat to older style connectors in car).

The wiring for the motors and seat belt sensors is all pretty straightforward and almost like for like, it’s the seat heating that’s the awkward bit.

I haven’t wired my heated seats up as yet, however I do have the colour map somewhere. I’ll look for it and post it here.

 

[Mac_Gaz]

Seat heating wires...

 

[Z3_Irish]

Cheers, luckily the seats I currently have will be worthless so going to try the full base swap and see if easy enough but if not then will just splice the wires together using your coding, cheers

 

[mrscalex]

It's a common mis-understanding that BMW make adapters to fit a pre-facelift seat into a facelift car. They don't as @Mac_Gaz says.

The adapters are to fit a facelift seat into a pre-facelift car. Why? Because BMW want or need to sell you a facelift seat for all cars to avoid maintaining multiple seat inventory - I would guess. They have no obligation to help you retro-fit old seats into a newer car.

My advice would be to swap the entire base over if it's all plug and play cables. I can't remember. The thing is the heated seat wiring and stop sensor cables live on the seat top and connect to the base. Also the seat belt pre-tensioner cable feeds through the lower seat cover as a form of cable management (on a Sport seat anyway).

The only slightly tricky part is the back rest adjustment that works off two bowden (cycle brake) cables. But their presence can be initially alarming rather than difficult to work on. The trick is the cables need to be fed in and out through the frame with it held up half-way but not mounted - or dismounted. At the same time you need to unclip/clip the nipple and bracket into place that attaches to the seat base. You'll also have to dismount the side-plastic with the lever to get the required slack. When you put it back make sure the cable loop is mounted on the lever.

Alternatively you can make up your own adaptor cable which is what I've done before. You'll need the floor mounted connectors cut off a scrap pre-facelift car. I can help with that if required. These go into the underside of the seat.

And a donor cable from another BMW (eg X5) with the yellow connector that normally hangs off the facelift seat underside. No one is likely to chop an actual Z3 connector off a seat for you. Then it's down to your wiring skills tracing wiring and splicing it together with the aforementioned loom section. I like this approach as it's all reversible.

Note the yellow block is configurable with different sub-plugs. You may need to reconfigure the pins to make everything work. BMW sell the pins as a spare part if required.

So donor X5 cable (try and get one cheaper than this - I paid £11 each incl. shipping). You only want the yellow block and as much cable coming out of it as possible.

https://www.ebay.co.uk/itm/252228712217

This will plug into your floor connector that looks like this.

I think there is probably more than one type of facelift wiring harness on a seat underside.