[YucA]

Recently noticed the passenger side seat was twisting when attempting to slide it front or back. Quick google showed me each side was connected by a flex cable which reminded me of my old e39 m5 seats twisting. Luckily, this was an easier fix and managed to do it with the seat in the car and leaving it plugged in.

If you plan to do this and want to work more comfortably by removing the seat, make sure you disconnect the battery before unplugging the large yellow connector under the seat. MOST of the time this saves you from having to clear SRS codes. If not, just be aware you will have to clear codes.

Seems like the plastic cross bracket isn't a part officially sold by BMW; I wasn't able to find a part number, but was happy to see there were plenty of offerings on eBay and Ali. Pulled the trigger on one from eBay for ~$20.

Part in question (or search for "Seat Adjustment Slide Rail Bracket for BMW F30"):
https://www.ebay.com/itm/286212336893

I started by aligning and sliding the long flex back into the motor to be able to properly slide the seat back and forth to remove the T50 bolts holding down the seat. Flex cables were in perfect shape in my case so I had no issues with the adjustment needed here. Just had to keep one hand holding the motor and broken pieces to make sure the flex would stay put. They do sell the part that broke with new flex cables as well if yours got chewed up for whatever reason.

After the 4 T50's are removed, I leaned the seat back to assess the situation. Each end of the plastic bracket that broke is held in by two plastic push pin tabs. Flat screwdriver or plastic tab removal tool pops em right off and you can remove the parts. Make sure to unplug the connector going to the motor.


Motor pops up and slides out, goes back in the reverse. It's self explanatory, once you have it in front of you.




To re-install this bracket you will need to remove one of the seat rails. I removed the outer one closest to the door, two bolts and it drops. You also need to remove the plastic trim cover, has a few tabs you can see from under to pop it up, forward and out. Be aware that the bolts are keyed. For the front, remove the 13mm nut facing out; as the bolt keyed, you don't have to worry about holding the bolt down, but be aware the front bolt and nut can come out. For the rear, you must loosen the 19mm nut which is captured; it rotates, but won't fall out. The bolt will come out from the outside.

This is the rear bolt, you can see the key/notches that hold it from spinning:


This might be a little OCD as I'm sure eyeballing it would be enough, but I pulled out my calipers and made sure both rails were aligned:




At this point, I took the opportunity to clean both rails, carpet, everything! I stopped taking pics after this point as I was just trying to finish. Now, I'm going to have to clean the drivers side well too... You may also want to add some grease to the lead screws if it looks extra dry.

I first attempted to re-install the plastic bracket by aligning the shorter shaft with the motor first (inner rail). This didn't end up working out as it was a PITA to align the longer flex while holding it all up.

I ended up installing the plastic bracket on the rail I removed, aligned the plastic sleeve in the track of the plastic bracket and made sure to have the other end sitting in the motor first, then aligned the shorter flex into the motor by twisting the plastic bracket enough for it to seat itself enough to be able to screw the 19mm nut into the bolt of the back of the rail, then did the front bolt and 13mm nut. Also note, both of these bolts had red loctite. If you have any on hand, dab a bit.

Plug the motor back in and make sure it slides correctly. Tighten the 19mm nut in the rear and the 13mm nut in the front; align the seat and reinstall the T50 bolts and you're done!