Power seat: Slide function not working.

[E39 Sean 540ia]

Recently my passenger power seat stopped working. It does not slide forward or backwards however the headrest goes up and down and the tilt/ up and down function works properly. I really cannot find any information on this, only seat-twist DIY's. Every old link I click on does not work anymore so thanks for any help in advance.

First off, the seat is all the way backward so I cannot remove the seat. The two rear bolts are covered. I have to find a way to fix this with the seat still attached, no room to work I guess, yay!

Earlier today I looked under the seat to see what I was messing with. I noticed a two pin plug hanging there with two wires attached, one blue, one white. The two wires come from the rear of the seat and lay on the centerline. I have literally spent most of my day under the seat with a flashlight, no luck finding where this goes.

One question that would help me greatly is which motor under there deals with the sliding function(forward and backwards)? Any other suggestions or tips would be great as well.

[dmp 5]

Hi mate

Sorry cant help you with which motor to replace. But I'm sure the seats can be removed out of the car, as i did this when I recently changed to comforts seat. There was only 4 torx screws holding the seat down. The rear screws were covered by a plastic trim, which pops of to reveal the screws.

hope this helps.

[E39 Sean 540ia]

I wish I could get to them. They are covered by the seat (which is all the way backwards). The screws are on the rail and yes you have to remove the plastic cover which I cannot get to either. Thanks though that would be the best thing to do but it doesn't seem possible with the seat back.

[m5hoot]

If you hear the motor running when you try to move seat forward, you have a variation of seat twist-same issue. Search seat twist ONLY if you hear motor trying to move seat. This is an easy cure regardless of whether you hear motor running or not.

[E39 Sean 540ia]

Seat twist deals with the reclining function of the seat. One side will recline the other side does not, usually the "backrest track" is just out of whack or something like that. I am trying to get my seat sliding forward and backwards. I really do appreciate the help but I think it's a separate motor or set of issues that deals with forward/backwards movements (not sure though).

I don't hear anything when I press the switch.

[E39 Sean 540ia]

I finally got some free time to work on my seat again. I didn't really get anywhere though, I have removed the switch cover on the side and have the seat fully tilted. These are some quick pictures I took of the plug in question:





The wire comes from the rear and right on the center line of the seat. If anyone could tell me where this plug goes it would be greatly appreciated.

Everything seems to be plugged in. I have looked under the seat from every angle I possibly can. I don't even know where to start.

[caryalon]

That looks like the passenger seat occupancy sensor mat plug. Is your airbag light on?

[E39 Sean 540ia]

That looks like the passenger seat occupancy sensor mat plug. Is your airbag light on?

Yes the light has been on ever since I had my car at the dealer for something... don't remember what for.

Do you think that would cause my seat to not have forward and backwards adjustments?

[jstern]

I just had both front seats out of the car to remedy the seat twist malfunction which has to do with seat back control cables. So I was intent on the cables and not the seat slide (forward/backward) function but I did notice the following. There is an electric motor in the middle of the seat bottom-approximately centered front/back and side to side-that turns a shaft that has gears on each end. These gear wheels act on the geared rails that run to the front and rear of the seat.

I did not see how that motor was attached to the seat. With the seat front adjusted all the way up and the front torx bolts removed so you can push the seat a little higher, maybe you can figure out how to unbolt that motor from the seat. If you get the motor out, you can probably push the seat forward by hand and get to the rear torx bolts.

Good luck.

Edit: After looking at some pics of the seat bottom in the seat twist DIYs, I see that my memory of the location of the fore/aft motor is faulty. The unpainted metal bar in your pictures in this thread, is the bar that turns the geared wheel on the side opposite from the motor. The motor is located in the middle of the seat front/back but is all the way over on one side attached to a gear box. You'll have to try and figure out how to remove the motor. Maybe looking at the pics on some of the seat twist DIYs will help you.

[E39 Sean 540ia]

I just had both front seats out of the car to remedy the seat twist malfunction which has to do with seat back control cables. So I was intent on the cables and not the seat slide (forward/backward) function but I did notice the following. There is an electric motor in the middle of the seat bottom-approximately centered front/back and side to side-that turns a shaft that has gears on each end. These gear wheels act on the geared rails that run to the front and rear of the seat. I did not see how that motor was attached to the seat. With the seat front adjusted all the way up and the front torx bolts removed so you can push the seat a little higher, maybe you can figure out how to unbolt that motor from the seat. If you get the motor out, you can probably push the seat forward by hand and get to the rear torx bolts. Good luck. Edit: After looking at some pics of the seat bottom in the seat twist DIYs, I see that my memory of the location of the fore/aft motor is faulty. The unpainted metal bar in your pictures in this thread, is the bar that turns the geared wheel on the side opposite from the motor. The motor is located in the middle of the seat front/back but is all the way over on one side attached to a gear box. You'll have to try and figure out how to remove the motor. Maybe looking at the pics on some of the seat twist DIYs will help you.

Thanks jstern, from looking under the seat I can see three motors. There are two on both sides left and right, right towards the front of the seat that lay by the rails.And 1 centered in the very front almost tucked up under the front of the seat that is attached to the seat bottom.

I have been looking at seat twist DIY's and a seat occupancy mat DIY thanks to caryalon but I see where that is plugged in so I don't think it is the issue.

I did wonder if I removed both of the front motors if I would be able to push the seat forward. I think I'm going to try it now. I have a miniature wrench that uses torx bits and is literally like 2 inches long. So that is going to help.

After school I will try to take pictures of all the motors to help clarify things.

[jstern]

The front motors control the seat back and not the fore/aft travel of the seat. If you look carefully with a mirror, you will see the black cables that run down the sides of the seat bottom and plug into those front motors.

The key to locating the motor that controls front/back movement is the unpainted steel bar that runs the width of the seat-the one showing in both your pics. That is actually the drive shaft for the geared wheel on the side of the seat opposite from the motor. The motor is attached to an aluminum gear box and is just in front (of the car) of the bare steel drive shaft. If you look at your pics at the beginning of this thread, you can see one end of that motor just in front of the steel bar on the left side of the pic.

[E39 Sean 540ia]

If you look at your pics at the beginning of this thread, you can see one end of that motor just in front of the steel bar on the left side of the pic.

The motor in that picture is one of the two motors towards the front that I mentioned.

Here are some pictures of the three motors so we can be on the same page:

Left:

Right:

The one in the front almost tucked up under the seat:

It seems that the motors are plugged in how they are supposed to be. Only clue that something is wrong is the wire hanging down(and the seat doesn't work haha).

The key to locating the motor that controls front/back movement is the unpainted steel bar that runs the width of the seat-the one showing in both your pics. That is actually the drive shaft for the geared wheel on the side of the seat opposite from the motor. The motor is attached to an aluminum gear box and is just in front (of the car) of the bare steel drive shaft.

Thanks I will look into this and see if I can understand it when I'm looking at the seat.

[jstern]

My best guess is the left side motor. The first in the last three pictures.

Just to make sure the fuse is good, check fuse #10 in the glove box. I'm pretty sure it's good because you said the head rest up/down was working but I'd check it anyway. If possible check the fuse with a multimeter-sometimes they look OK but are not. If no multimeter, swap in a fuse of the same value as a test.

One more thing to test: If you can reach that unpainted shaft under the seat, you could try and twist it with your hand or a plier. maybe the seat would move if you did that.

If you look at the last pic in this thread:
https://www.bimmerfest.com/forums/sh...45&postcount=8
you will see a good image of the seat movement motor and the shaft on the left side of the picture.

[E39 Sean 540ia]

Thanks a lot jstern. The last picture in that thread really cleared up what you were saying. I though that shaft connected to both motors. Now what you said makes more sense. I'm going to give it a try this weekend and then update.

[jstern]

Hey! Good luck, Sean. What a PITA!

John

[caryalon]

Yes the light has been on ever since I had my car at the dealer for something... don't remember what for.

Do you think that would cause my seat to not have forward and backwards adjustments?

Nope, that would cause the airbag light. Wouldn't have anything to do with the seat motors. You either have a faulty connection in the wiring loom/connector(s), or a bad motor.

[E39 Sean 540ia]

Ok so I removed the motor:

Now I'm stuck again. The seat still cannot be moved manually and the drive shaft(metal bar in picture) cannot be spun manually either. I'm starting to look for a new motor. I'm going to see if I can test this one first.

[caryalon]

How about taking a vice grips or pliers (smooth jaws would be best) and turning that post that's sticking out of the (i think) gear body. It'll probably move the seat very slowly, so you may have to turn it a lot of turns, but it should move the seat if that's the right motor.

[E39 Sean 540ia]

That is what I was going to try next. Thought I would ask first though, thanks.

[jstern]

Congrats on getting the motor out. You should test the motor but you should also test if you have power at the motor plug when you press the seat movement switch. If not, you have to test for power at the input part of the switch, and if you do, test for power at the output of the switch. I assume you have tested fuse 10 above the glove box.

[E39 Sean 540ia]

Congrats on getting the motor out. You should test the motor but you should also test if you have power at the motor plug when you press the seat movement switch. If not, you have to test for power at the input part of the switch, and if you do, test for power at the output of the switch. I assume you have tested fuse 10 above the glove box.

I checked the fuse and it didn't look blown, I have no tools to test electrical. If I find some more info on troubleshooting and testing electrical components I might give it a try and buy some tools.

For now though, I will move the seat forward by turning the thing the motor goes on(which does work, slowly). At least then my seat will be where I want it.

[E39 Sean 540ia]

Just picked up a tester:



Now I just need to learn how to use it.

[E39 Sean 540ia]

I hooked up the test light to the negative post on my battery.



Then I pressed the test probe into each wire(one at a time of course) on the plug that hooks into the motor.



When I tested the red/yellow wire by pressing back on the switch the test light lit up.
When I tested the yellow wire by pressing forward on the switch the test light lit up.

I'm guessing that means I have power to both my forward and backward adjustments. However they still don't work so I think my motor is bad. Can anyone confirm that?

Does anyone know how I can test the motor?

[jstern]

Your test does confirm that you have power to the motor connector.

After studying the electrical diagrams in the Bentley Manual, the seat motor works by one wire being the ground and the other being the power depending on which way you command the seat to move using the switch. So you can test the motor by powering one wire and grounding the other. I would test the motor both ways so you can be sure the seat will move both frontwards and backwards. You can push a needle through one of the wires for your connection.

BTW-I see that you poked holes in your wires which is OK and which you will probably have to do with the motor. The thing is that you want to seal those holes so moisture does not get into the wires and cause the copper in the wire to corrode-more problems down the line. I've found that the best, and simplest vway is to use liquid electrical tape. It comes in a small can with a brush in the lid and it is very effective. Just follow the instructions on the bottle.

Also test lights, like the one you bought, are effective but can cause problems when testing some computer wire. Multimeters are really not very expensive and are, in many cases, safer to use than a test light although test lights do have their advantages.

[E39 Sean 540ia]

Your test does confirm that you have power to the motor connector.

After studying the electrical diagrams in the Bentley Manual, the seat motor works by one wire being the ground and the other being the power depending on which way you command the seat to move using the switch. So you can test the motor by powering one wire and grounding the other. I would test the motor both ways so you can be sure the seat will move both frontwards and backwards. You can push a needle through one of the wires for your connection.

BTW-I see that you poked holes in your wires which is OK and which you will probably have to do with the motor. The thing is that you want to seal those holes so moisture does not get into the wires and cause the copper in the wire to corrode-more problems down the line. I've found that the best, and simplest vway is to use liquid electrical tape. It comes in a small can with a brush in the lid and it is very effective. Just follow the instructions on the bottle.

Also test lights, like the one you bought, are effective but can cause problems when testing some computer wire. Multimeters are really not very expensive and are, in many cases, safer to use than a test light although test lights do have their advantages.

I don't really know how to give power to something so that sounds confusing as hell. I understand that your saying one wire can be both ground and power depending on direction of switch adjustment. But how do I give power and ground, Do I use a battery? from a car?

Thanks a bunch. Ill get some liquid electric tape. I've been real busy with school so I haven't done much yet. I have the seat where I want it now though. I turned the post like 1000 times.

Yeah I read some scary stuff happening to people, figured a test light would be OK for seat motors and such things though. I don't plan on using it for anything else.