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SOLVED: interior back seat buzz/rattle while driving and listening to bass

Figured I'd share some findings.

TL;DR: backseat buzz during driving / loud music solved, root-caused to manufacturing issue, easy fix.

About a month of ownership of my Model 3 (delivered 8/4/18), a buzz / rattle appeared in the back seat. It tracked with rolling over bumps / potholes, but also with loud bass-heavy music. Drove me nuts - not what I expect after dropping $89k on a car.

I used the iOS Signal Gen app to stream a tone over bluetooth to the car at max volume, and narrowed the resonance down to the back seat at ~38.4 Hz. I could press against the middle rear seat armrest and make it go away, but as soon as I let go with armrest in any position, it returned.

Started taking the armrest apart step by step while playing the tone, to see where the issue was. Had to take most of it apart and got down to the issue:

The metal rod that keeps the rear left seat's leather lining attached to the seat was not routed fully through the cloth loops, nor the terminating metal hook in the seat back! Looks like a manufacturing quality oversight.

Here's the process. Between each step I kept the tone generator running to see if any particular step made the rattle go away.
  1. Remove rear middle headrest by inserting a small L-shaped allen wrench into the hole of one of the post mounts
  2. Pull up on the headrest while pressing allen wrench into the notch
  3. This will clear the retention notch on the headrest post and allow you to remove it
  4. Twist and pull up the post mounts - they come out pretty easily
  5. Use a T45 bit to unscrew the armrest pivot bolt.
    • Careful, there's a plastic washer between the armrest and the metal hinge that might fall out and is easy to lose!
  6. With bolt removed, armrest can be wiggled out of place at an angle
  7. Removing the black plastic cover in the middle seat was the toughest part. Prying around its edges with fingers revealed 3x retention fittings. Applying an uncomfortable amount of force allowed the black plastic plate to come loose while leaving the white fittings in the metal backing.
    • Once the cover was off, I could easily feel around and see that the rattle came from the metal rod meant to retain the seat lining.
    • It was not looped through the bottom 2x loops of the fabric, nor the metal clip at the very bottom. This clip is what the rod vibrated against at resonance!
  8. Re-route the rod through the fabric loops and metal hook at the bottom
  9. Reassemble! Pry the 3x plastic fittings out of the metal back and replace if damaged (kits like this one have them) and place them into the black plastic cover's notches. It's much easier to re-insert this way.
  10. Press the black plastic & fittings back into metal back, screw the the armrest back in (mind the washer!), and pop the headrest mounts & the headrest itself back in!
Rattle: gone!

Attached visual steps of the process!

Hopefully it allows someone to get rid of an annoying buzz. I've fed the info over to Tesla's manufacturing and engineering QA... hopefully it helps them too!
 

Attachments

  • Seat Rattle.jpg
    Seat Rattle.jpg
    1.3 MB · Views: 505
@krizzle, I have not found it. I did try the sound generator very loud, but never got a vibration going. I think my problem is more metal on metal when it's cold. Maybe a rivet missing. I'm waiting for time to have someone in the back seat when it's cold listening to pinpoint it. I recorded it while driving, but it's not easy to tell from that what the sound is. It's a creak over a bumps when it's cold.
 

SMAlset

Well-Known Member
Mar 4, 2017
9,287
10,154
SF Bay Area
Figured I'd share some findings.

TL;DR: backseat buzz during driving / loud music solved, root-caused to manufacturing issue, easy fix.

About a month of ownership of my Model 3 (delivered 8/4/18), a buzz / rattle appeared in the back seat. It tracked with rolling over bumps / potholes, but also with loud bass-heavy music. Drove me nuts - not what I expect after dropping $89k on a car.

I used the iOS Signal Gen app to stream a tone over bluetooth to the car at max volume, and narrowed the resonance down to the back seat at ~38.4 Hz. I could press against the middle rear seat armrest and make it go away, but as soon as I let go with armrest in any position, it returned.

Started taking the armrest apart step by step while playing the tone, to see where the issue was. Had to take most of it apart and got down to the issue:

The metal rod that keeps the rear left seat's leather lining attached to the seat was not routed fully through the cloth loops, nor the terminating metal hook in the seat back! Looks like a manufacturing quality oversight.

Here's the process. Between each step I kept the tone generator running to see if any particular step made the rattle go away.
  1. Remove rear middle headrest by inserting a small L-shaped allen wrench into the hole of one of the post mounts
  2. Pull up on the headrest while pressing allen wrench into the notch
  3. This will clear the retention notch on the headrest post and allow you to remove it
  4. Twist and pull up the post mounts - they come out pretty easily
  5. Use a T45 bit to unscrew the armrest pivot bolt.
    • Careful, there's a plastic washer between the armrest and the metal hinge that might fall out and is easy to lose!
  6. With bolt removed, armrest can be wiggled out of place at an angle
  7. Removing the black plastic cover in the middle seat was the toughest part. Prying around its edges with fingers revealed 3x retention fittings. Applying an uncomfortable amount of force allowed the black plastic plate to come loose while leaving the white fittings in the metal backing.
    • Once the cover was off, I could easily feel around and see that the rattle came from the metal rod meant to retain the seat lining.
    • It was not looped through the bottom 2x loops of the fabric, nor the metal clip at the very bottom. This clip is what the rod vibrated against at resonance!
  8. Re-route the rod through the fabric loops and metal hook at the bottom
  9. Reassemble! Pry the 3x plastic fittings out of the metal back and replace if damaged (kits like this one have them) and place them into the black plastic cover's notches. It's much easier to re-insert this way.
  10. Press the black plastic & fittings back into metal back, screw the the armrest back in (mind the washer!), and pop the headrest mounts & the headrest itself back in!
Rattle: gone!

Attached visual steps of the process!

Hopefully it allows someone to get rid of an annoying buzz. I've fed the info over to Tesla's manufacturing and engineering QA... hopefully it helps them too!

Wow that’s really clever sleuthing!
 

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