SL (129) seatbelt locking up problem

[jefft]

Hi,

Has anyone an idea what could be causing this problem?

The driver's seatbelt on my 500SL (129 model) reels out fine and the inertia reel behaves as normal, until the belt is locked into the latch as if in use, at which point the reel seems to lock up and won't let the belt play out at all, even slowly. Bit of a nuisance, being pinned back to the seat all the time! The passenger's side belt is fine.

I thought it might be related to a comment in the manual which says that the inertia reels will lock up if the power fails, but removing the relevant fuses makes no difference, nor does the ignition position, so I think I've ruled out power supply issues. Another thought - would the pretensioners have some control over the reels in this way?

Happy to do a bit more diagnosis myself, if anyone knows how to get into the seats on a 129 - there's no obvious point of entry to start dismantling the things!

Cheers,


Jeff

 

[stats007]

There is a mechanical Bowden cable that allows the reels to operate when the belts are not clipped in to the buckle. The relays K18/2 & K18/3 are operated by the roll bar control unit - when they lose power they lock.

 

[jefft]

Thanks, Stats... I'll have a look at those. Any idea where those relays are in the car? (I've never managed to find a workshop manual for a 129, sadly!)

Sounds like it could be a dodgy connection on the one seat, given they're controlled from the same place and the passenger side is fine. Rollbar works fine too, so the CU is getting power ok.

I think I saw a posting on one of the forums about how to open up the seat so that's some fun for tomorrow, I reckon.

Cheers

J

 

[jefft]

All sorted. Thanks for the clues!

A few quick voltage checks and half an hour tracing some wiring around the seats and all became clear... someone has replaced the buckle on the driver's seat previously with a different type (has 4 wires rather than 129's 2 wires) and bodged the connection to the existing wiring rather clumsily. That's resulted in the wiring chafing on the metalwork and eventually breaking. I guess that made the warning light wake up, as they've then unplugged both the buckle and the reel wires from the control unit under the seat. What a nasty piece of work!

So, a quick bit of soldering and plugging-in later and all's well.

Thanks


Jeff

 

[SL320Newboy]

Hi All,

Just to pick up on a point you made Jeff - does anyone have a link to a basic maintenance workshop manual for the 129? There must be one on the net somewhere!! (preferably a free download!!)

cheers

 

[jefft]

Workshop manuals

Nah, I've spent a load of time looking for workshop manuals and nothing out there. My local independent car parts shop has never heard of any either.



J