Electric seat fault - Highly annoying!!!

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phb10186
Joined: Sun 16 Sep, 2007 07:18
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  Z3 roadster 2.8
Location: London and Bournemouth

Electric seat fault - Highly annoying!!!

Post by phb10186 »

Just noticed that the passenger electric seat is not working any more... can only have been faulty for a couple of months I guess...

Checked fuse and its blown, and everytime I put another one in it keeps on blowing, OK so a short. Fathomed that much out, but I can't get to the electrics to test the seat, because its broken and stuck in the back most position... Remember reading about someone else who had this problem a while back.

How am I meant to get the seat forward enough to get to the rear bolts to remove the thing and test the electrics????
:!:
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1998 2.8 M52TU, pre-facelift, hard top, montreal blue, tan interior, 91K
estocks
Joined: Tue 04 Oct, 2005 23:36
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Post by estocks »

I don't know the answer, but be damn sure to unplug the battery when you are poking around in there otherwise the seatbelt pretensioner wires could be disturbed, triggering the airbag light.
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senna
Joined: Tue 21 Feb, 2006 13:33
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  Z1 roadster

Post by senna »

May be you could get under the car and drill out the bolts, should not be difficult.
You should be able to undo the front bolts?
I have Z3 seats, runners/motors. Will be putting on flea bay soon.
Engine Transplants by Night, Heart Transplants by Day. "you own the best Z1 in the world"
henrycrun
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Post by henrycrun »

In addition I believe the seatbelt pretensioner works with an explosive charge so you must disconnect the battery
phb10186
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  Z3 roadster 2.8
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Post by phb10186 »

sensors and airbag warning light A-OK, just can't get the bloody seat to move... this might suggest that the contacts are in order... but if there is no power to the circuit, who knows.

If I look under there, there is a white plug... was wondering if the forward reverse control is one of them, and then I could short it out some way.


Tried undoing the front bolts, it gives no extra space, its as if they were still in place.

There is no power at all, just blows the fuse as soon as I repllace it. As I said... Highly annoying.

Just don't want anyone to tell me that you cant access the contacts to the motors, you cant get to the bolts, and there is no manual over-ride. So, please don't tell me that! Cant beleive that there is no way of getting the seat forwars manually.... dealer tricks anyone?

Said it before, and I'll say it again... BMW electrics are crap (well compared to the Jap cars I have owned anyway).
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maxman
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  Z3 roadster 2.0
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Post by maxman »

The white connector is the seat movement connector plug if i remember correct (see Tony Cal web page)you use an aux battery to power the seat,the wire with the brown trace is the earth.I would disconnect the car battery first.
For anyone new the Tony Cal mods on his web page are a good source of info.
phb10186
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  Z3 roadster 2.8
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Post by phb10186 »

Hi Max,

OK, well there are 3 motors in the seat, forward is just one of them! So that white connector is one of those 3... hopefully when designing the car they allowed for this type of failure and put the one i need at the front there!

Could you link up the the website you are talking about, thanks.
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c_w
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Post by c_w »

Can/have you raised the seat for more access?

I'm not sure which motor is which but there are only two from memory as there are only two large plugs for powering them (have tested them off the car). I would just get a spare battery as suggested above and put wires from it to the connectors. Swap the wires over to reverse the motor.
maxman
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  Z3 roadster 2.0
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Post by maxman »

http://www.tony-bmwccse.co.uk/ Here is the website.Im pretty sure this connector controls all movement but i could be wrong as it is a while since i checked out some seats that i sold.
phb10186
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  Z3 roadster 2.8
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Post by phb10186 »

maxman wrote:http://www.tony-bmwccse.co.uk/ Here is the website.Im pretty sure this connector controls all movement but i could be wrong as it is a while since i checked out some seats that i sold.
can't find anything detailing seat electrics on there mate!
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phb10186
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  Z3 roadster 2.8
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Post by phb10186 »

maxman wrote:http://www.tony-bmwccse.co.uk/ Here is the website.Im pretty sure this connector controls all movement but i could be wrong as it is a while since i checked out some seats that i sold.
can't find anything detailing seat electrics on there mate!
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lurker
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Post by lurker »

I'm probably passing grandma a recently unwrapped egg for sucking practice, but the main reason everyone's saying to disconnect the battery is that there's a connector that goes into the seat that if you disturb (by disconnecting or discovering that the wires are frayed and about to snap) will trigger the airbag warning light. This should only happen if the keys are in but for safety disconnect the battery - not a great thing if you're trying to make the electrics work, but might help to have a 12v power source lying around.

go to the seat kebob fix site here: http://www.waycoolinc.com/z3/02/100602/shish01.html as it might help you.

Not sure how to get the seat forward without having the power but personally I wouldn't go under and drill the bolts out unless you have no other choice - it'd be a pain without a lift or pit and you might find you're removing captive bolts leaving you problems when you come to refit the seats... you could try applying 12v directly to the motors via some wires (after you've removed the front bolts) to be able to get to the rears....

best of luck

p.s. in case any use, my writeup of fixing the seat kebab thingy is here:

http://www.zroadster.net/forum/viewtopi ... light=seat

and the pics of under the seats are here:

http://www.boardie.com/pics/z3seat/
'98 Z3 2.8 Nottingham
If it moves and it shouldn't, use Gaffa Tape, if it doesn't move but it should, use WD40...
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Seats

Post by Guest »

There is non 'silver bullet' fix, but as the seats use a very simple control circuit, with a switch and no relays etc. you should look at a wiring diagram and all wil be clear. At a guess, the switch could be the source of your problem, as it has both neg and pos on its contacts.
phb10186
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  Z3 roadster 2.8
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Re: Seats

Post by phb10186 »

Mike Fishwick wrote:There is non 'silver bullet' fix, but as the seats use a very simple control circuit, with a switch and no relays etc. you should look at a wiring diagram and all wil be clear. At a guess, the switch could be the source of your problem, as it has both neg and pos on its contacts.

This is what I thought.... extremely bad design. I reckon its the switch too thinking about it... will check it out and report back. Knew the electrics were fairly simple.
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phb10186
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  Z3 roadster 2.8
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Post by phb10186 »

Right: this piece of news will save everyone here a fortune if they have this problem, and don't know this. If you know it, then its just a reminder.

The white plug that you can see mounted at the front of the seat as you look under controlls the forward/ reverse motor - so if you have a problem like mine, disconnect it and short it out with a 12v power supply and you will get forward or reverse depending on which way round you connect it.

So with my fuse problem, this at least will allow me to remove the seat and have a good look, and gain access to the wiring. So: as long as the motor itself is working, you can always move the seat back and forwars to allow it to be removed.

As far as Mike's switch suggestion, have had a look at the switch, and it looks verry complicated... don't know how I will test it, but I will find out.

will keep this updated... hopefully something very simple.
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phb10186
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  Z3 roadster 2.8
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Update!!!

Post by phb10186 »

Think this loom is the problem:

Image

I took the seat out and then removed the loom, tested both motors in the seat with my 12V supply and both work fine...

Tried to test the loom by connecting it up to my 12V supply with a 30Apm in line fuse just like it would be in the car, and it just blew the fuse.... so there must be a short in the loom I guess... probably the main switch.

The only thing I was wondering is that the seat is earthed to the car body when in the car, but obviously not when I just tested the loom... would this make any difference??? The symptoms are therefore, seat loom blows 30Amp fuse as soon as it's connected to 12V supply.... even when all the motors etc are disconnected.... so therefore it can't be anything other than the loom/ switch, can it?


Does anyone have an old seat that is past it who would be willing to sell me the loom... or a loom itself?

Otherwise its internet and ebay for me.

Switchgear is made by 'Cherry' the same people who make my keyboard, part number from the component is...

BMW 8 410 673.9 - just had a look on real OEM and cant even find the part!

BW

Ben
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Robert T
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Re: Update!!!

Post by Robert T »

phb10186 wrote:BMW 8 410 673.9 - just had a look on real OEM and cant even find the part!
The seat switch and loom is shown as a single part on RealOEM, but is listed under Vehicle Electrical System -> Switch rather than under seats. See this page for details.

Can't just see anything that corresponds to your part number, but it may be that the part has been superceded, as it says from 07/1997, so it will depend when your car was built (shown on the label on the front suspension tower).

There is almost certainly a short somewhere, either in one of the connectors or in the switch itself. A new loom and switch will set you back about £100 for a basic seat and £180 for a sports seats. Both are Z3 only parts. You would almost certainly be cheaper sourcing one from a car breaker - even if you have to buy a manky seat to get it.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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estocks
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Post by estocks »

I'd take a scalpel and gently remove all the black sire shrinkwrap, repair any faults. Rebind with electrical tape.

If you find no faults, measure/inspect each switch for faults.
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phb10186
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  Z3 roadster 2.8
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Post by phb10186 »

estocks wrote:I'd take a scalpel and gently remove all the black sire shrinkwrap, repair any faults. Rebind with electrical tape.

If you find no faults, measure/inspect each switch for faults.

Yeah, just taken the switch apart.... its completely blown inside, to the point where two of the rocker contacts have been welded together, so that explains the short, and there is no way I can repair that as far as I can see.... so yeah will need a new switch loom.... and it also smells like burnt plastic. Amazing what has happened inside, and also amazing how well the switch is made.... the circuit should be relay controlled to protect from this....

-B


So will be on the look out for an old seat I guess - does anyone know a good BMW breakers, hopefully in the London or surrounding area?
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estocks
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  Not specified

Post by estocks »

www.fabdirect.com


ww.gsfcarparts.com
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Use the Search button before posting newbie questions about hard tops and fitting kits, footwell speaker amps, water in the boot, hood maintainance and those horrific angel eyes. We get like 10 threads a week on the same subject, it's obvious that you haven't searched.
phb10186
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  Z3 roadster 2.8
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Post by phb10186 »

Ok fixed the seat today....

BMW quoted me £150 or so for the switch loom (switch is part of the loom and cannot be purchased separately).

I managed to find an off-side loom for about £30 on partsauction.co.uk but as you can imagine they are mirror opposites.

As you can see they just have the switch board mounted 180 degrees to one another.... so it is just a case of de-soldering it and then re-soldering it the correct way round, but with only one alteration for the up/down control (the small black plug)..... invert the wires on these two, and away you go.

Of course, you only have to do this if you have the wrong side and don't want to pay BMW dealer prices..... It was actually not that easy getting the part, as most breakers will only sell a seat as it, and don't want to break them down. So you might get stuck with this problem like me.

The picture is no good, but all I want you to see is that the wires come out of opposite ends, indicating 180 degree rotation for each respective side....

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henrycrun
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When (powered) seats go bad

Post by henrycrun »

Looks as if I have similar problem.

Went to move the passenger seat, but Minnie had left a drinks bottle in the footwell, now jammed under the seat. I was just relieved that I hadn't burst the top off.

Following morning - flat battery. Current drain measured at 3.5A Removed the fuse for now and charged the battery.
Bugger. As its not the drivers seat it will have to wait.

If BMW must fit powered seats, couldn't they design it so that the seats are just live at position 1 on the key ? Rant Over
phb10186
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  Z3 roadster 2.8
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Post by phb10186 »

Why arenn't they relay controlled like they should be....

Mine burnt out with the full 30 amps or whatever essentially welding the whole switch inside together, then it was just blowing fuse after fuse all the time.

Just replace the switch loom, and it will be fine..... I've said this before.... BMW electrics = crap.
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mattdedasc
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Post by mattdedasc »

I have the driver's seat forwards-backwards motor jammed, or broken. Basically, the seat won't move in that direction.

Luckily it is in my usual driving position, but I have a MOT next week.

Will it fail the MOT for that?

Thanks
henrycrun
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Post by henrycrun »

Only if the MOT tester is vertically challenged :wink:
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mattdedasc
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Post by mattdedasc »

I still need to fix the blown motor (that's what I think it is).

Does anyone know how much will I have to fork out to sort the forwards-backwards movement?

thanks
henrycrun
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  Z3 roadster 1.9
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Post by henrycrun »

Someone on here said they just unjammed the motor or screw somehow. No idea what tools used or how you get access though....
phb10186
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Post by phb10186 »

I bet the motor works, and it's just a switch/ connection problem.... have you checked this out by trying to power up the motor from a 12 volt Supply???

You will have to raise it as high as possible.

If it has gone, that might be tricky!

You might be able to disconnect the driveshafts from the motor and turn them somehow.....

If you have to sacrifice the seat (last resort ONLY) try to maintain the seat itself and only cut away at the frame, at you could then get a replacment from any seat, and it will work.
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cdavie2002
Joined: Sun 16 Dec, 2012 10:52
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  Z3 roadster 2.8

Re: Electric seat fault - Highly annoying!!!

Post by cdavie2002 »

Hi All.

Ok, similar issue.

I removed the Drivers Seat years ago to deal with the 'slop'. The forward/back was working & never bothered to troubleshoot the up/down - the motor does attempt to move the mechanism, a clink can be heard. This will just need stripping & cleaning.

However the passenger side does not work at all. Today I removed the seat and tested with a battery. Again it functions forward/back as it should. But when installed in the Car - nothing.

Both fuses 5 + 19 are good. I swapped them over and the DS still works, and the PS does not....

The seat is still out, and I cannot seem to get 12v from the main white connector, I assume I should..?

Any thoughts/guidance would be greatly appreciated.

Thanks,
Chris
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