W124CE pass seat back won't lock

[Db7gtgrigio]

Hello

Have used this resource a lot to keep my 90 300CE-24 COUPE running well but have not yet posted. I have an issue that I cannot find any relevant posts in the achieves and would appreciate any suggestions. There are posts about the general issue but do not seem relevant to my circumstance.

Passenger front seat (RHD) will not lock in position when it should. Drivers side locks when engine on doors closed etc. I have checked the vacuum lines under the rear rest squab there is plenty of vacuum. The head rests deploy as they should (also vacuum controlled) and as I say the drivers side is fine.

I removed the hoses to the seats at the take off under the rear seat and applied a vacuum using my mity vac. On the drivers side I could see the locking mechanism moving as I applied vacuum. Once I got to about 85psi the mechanism moved no further. It moved far enough to lock the seat back in place. The vacuum held steady at 85psi.

When I tried it on the passenger seat the locking mechanism moved only slightly. Not enough to lock the seat back. The vacuum also held steady at 85 psi.

The fact that the vacuum held steady at 85psi seems to suggest that the diaphragms are not leaking. The problem therefore seems to be mechanical. Something is causing the vacuum to not pull the mechanism sufficiently to engage with the locking bar? the locking bar is rotated on a shaft by a cable that is obviously pulled by the diaphragm when under vacuum. There does not appear to be anything impeding the rotation of the locking mechanism and the cable looks clean and seems to pull smoothly for the short distance it is actually moving.

Any ideas?

Chris in sunny Sydney Australia.

 

[brigadier]

Hi! Could some wd40 around the locking arms help?

 

[Db7gtgrigio]

Hi! Could some wd40 around the locking arms help?

Thanks for the suggestion. I have tried that. The arms seem to move fine when I move them manually. In fact, the arm near transmission tunnel moves fine when the engine is turned on. It is the door side arm that does not move properly.

The arm is actuated by a cable which must be pulled by a vacuum diaphragm. The only thing I can think of is that the cable is not pulling properly. Perhaps it is binding??????

I will have to remove the seat I think to see how it is working and perhaps lubricate the cable.

Anyone have a reference for seat removal?

 

[grober]

http://www.w124mbci.com/W124HandBook/CD2/Program/Chassis/91-115.pdf
cables


http://www.w124mbci.com/W124HandBook/CD2/Program/Chassis/91-110.pdf
front passenger seat removal

 

[Dieselman]

Is the cable out of adjustment so the diaphragm runs out of travel before the cable pulls the mechanism?

 

[Db7gtgrigio]

Is the cable out of adjustment so the diaphragm runs out of travel before the cable pulls the mechanism?

No it does not appear so. I can manually pull the hook down to engage the bar, so there is obviously enough cable. It is just that when vacuum is applied the hook does not move far enough. It only needs another 5mm or so and the hook would then engage with the bar. TBH I am a bit unsure about my hypothesis that the cable is binding as when I manually move the hook I do not need to force it and the movement is quite smooth..........

Can't fathom this. The diaphragm takes and holds 85psi of vacuum, is moving the hook near the transmission tunnel a decent amount but hardly moves the hook near the N/S door sill. surely it can't be a vacuum issue but is a mechanical issue between the diagorapgm and the hook (which is the cable)

Anyone know how to remove the fragile looking trim on a coupe that covers the seat runners ( so I can access the seat mounting screws)?????

 

[grober]

Just unclips IRRC-use a soft surface wedge to lever it off carefully---- it helps to remove the guide rail along with the seat by unbolting the guide rail mount at the rear on transmission tunnel http://www.w124mbci.com/W124HandBook/CD2/Program/Chassis/91-100.pdf