Seat trouble

[Dusterbd]

Figured id fix the drivers seat before cleaning, so i could actually reach the pedals.

It has seat twist (easy enough)

The problem is that it is the entire way rearward in its movement. Every other function at least tries to work. The headrest goes up and down, seat bottom tilt, backrest (with twist limitations). Just no fore/aft movement. The motor doesnt make any noise, no vibrations, nothing. Checked for 12v, which it has on both the brown and red wires. So i doubt fuse. There seems to be only 1 plug, and that is the 3 wire directly to the motor.
I pulled the switch from a junkyard seat, and exact same problem.

What am i missing? Theres a 5 wire connector of 22 gauge wire that doesn't go to anything near the seat switch, and a 3 wire underneath the seat. However, theres no corresponding male connector for either that i can find.

I have to move the seat forward to get to the rear bolts to be able to remove the seat.

What am i missing????

[Dusterbd]

so. fpund the problem. it sppesrs the diode inside the ,odule mounted to the motor has failed. ive tried googling the bosch part number, and havent found a replacement. the motor operated in both directions when powered directly to the soldered leads. the tracks have not moved manually at this time, however. im about to remove the gearbox and see if theres any more damage.

20180731_153310 by Michael Crawford, on Flickr

20180731_153303 by Michael Crawford, on Flickr

20180731_151055 by Michael Crawford, on Flickr

is there a source for this module? or is it a $200 motor replacement/find good used are my only options? honestly, id be half tempted to power the motor directly, set the seat where I want, and forget about it, but id rather fix it properly than rig it.

[JimLev]

Are you sure that a diode? If it's not a zener diode you can probably replace it with just about any general purpose diode.
Check those 2 transistors above the diode in your pic.

[Dusterbd]

Honestly, im not certain if it is a diode, transistor, or flux capacitor. Never been any good with circuit board work.

Id be more than willing to try a replacement of the component if we can figure out what it is, because after all, i cant break it more than it already is.

In other news, straight wired the motor to my power supply on the bench. Works just fine to operate the tracks, so gears and such are fine. It really is just the circuit board.

[geargrinder]

Iz a resistor. Diodes are typically pretty tiny and have a square package. That bigger cylinder type package is typical of an SMD resistor, specifically a "MELF" package (full disclosure, I've used those before but had to look up what they were called! I'm gonna call 'em "MILF" resistors from now on...)

http://www.resistorguide.com/resisto...-and-packages/

Trick is the color code obviously is burned off it. If you can find the exact same component on another motor in the seat, you could order it from Mouser, you'd want to measure the size, then you could get the right MILF's showing up. If you can get the color code properly then between the size and value it should lead you to the right thing.

http://www.resistorguide.com/resistor-color-code/
http://www.resistorguide.com/resisto...de-calculator/

https://www.mouser.com/Passive-Compo...5g9n?P=1y95jjo

Of course the questions are always - like fuses - "why did it blow, cuz resistors don't just blow themselves up"... Lead guesses would be wiring shorts, or another failed component on the board, or a shorted motor winding... I dunno if a jammed switch (or a dumbass user holding the button down) could burn out a component like that...

Honestly I'd prob just go junkyard part myself, if you find a really crappy junkyard seat the place might let you have it super cheap... I once bought a super crap JY seat on purpose (just to drive on for a week or two as I refin'd mine..) and they let me have it for peanuts... I passed on a set of old 530i comfort seats from a friend some time ago just because they are such a PITA to store, otherwise I'd have a motor for you...

[Dusterbd]

Hmmm.....
Good question about why it fried. I really have no idea how it blew.

[Dusterbd]

as a follow up: was able to source the module and a new seat switch from a junkyard. 2002 530i was the donor. i replaced the seat switch due to the fact that the buttons dont line up with what they are supposed to do. in other words, the controls are very wonky and not easy to use. so i replaced the switch. and got the exact same problem.

im wondering now if some of the 3 wire connectors to the motor modules got swapped around somehow at some point. particularly the seat tilt and seat back recline leads. when im released from my prison (my wife has me in quarentine due to the flu) ill check that first. but im open to other ideas!

[Joe///540i]

I have a similar problem and will be curious what your fix ends up being.

The height adjustment motor only engages for a half second with every push or pull on the switch. So the motor moves the seat in tiny increments but it takes 20 pulls to raise it up to where a short person might like it.

I also tried a new switch with no result. I don’t think it’s the motor.

I hope you find something for me to try.

[geargrinder]

Dusterbud - have a close inspection at your connectors. I had an absolute brainbreaker of a PITA with my drivers seat at one point, turned out a pin in the seat connector was bent over and shorting to another pin intermittently. When it shorted it'd take out the P-bus so other stuff would stop working, when it didn't short everything would work OK... You don't have the exact same problem but maybe something is shorting under there...

Joe - I think the motors have overload protection so it could be something in the seat is bound up and the motor stops because it thinks its jammed. Id prob take the seat out, pull the cables in question and run them w/ a cordless drill to see if the mechanics all run smoothly... BTW you then can also run the seat on the bench w/ bench power supply (hint: jump pack + a junkyard seat connector works great) and inspect it while it operates to check for voltage and mechanical problems..

[Joe///540i]

Joe - I think the motors have overload protection so it could be something in the seat is bound up and the motor stops because it thinks its jammed. Id prob take the seat out, pull the cables in question and run them w/ a cordless drill to see if the mechanics all run smoothly... BTW you then can also run the seat on the bench w/ bench power supply (hint: jump pack + a junkyard seat connector works great) and inspect it while it operates to check for voltage and mechanical problems..

Thanks for the input, I appreciate it. I did repair the seat cables for height as well as incline/recline. I only had to repair one cable for height and thought for sure this was why the motor was cutting out quickly because of the reasons you referenced. I was surprised after repair that it still did it. It goes up straight now but slowly! Yes, the seat moved fine with a drill.

[computiNATEor]

Thanks for the input, I appreciate it. I did repair the seat cables for height as well as incline/recline. I only had to repair one cable for height and thought for sure this was why the motor was cutting out quickly because of the reasons you referenced. I was surprised after repair that it still did it. It goes up straight now but slowly! Yes, the seat moved fine with a drill.

Is it possible the un-repaired cable is binding?

[Joe///540i]

Is it possible the un-repaired cable is binding?

That is certainly a possibility. It does move the seat though?

[McKennaM]

There also the gearbox with a small plastic gear which has been known to break, I found out about it on the youtube. Do a search. The grease in the gearbox dries out and if you use the tilt a lot it could be the gear or the electric motor.