S124 230TE Tailgate Closing Assist Problems and lock replacement.

shj124

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Dec 17, 2018
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Location
London
Car
S124
Several months ago the tailgate lock on my wife’s S124 230TE started playing up. The electric closure assist would carry on cycling every two to three seconds even when the tailgate was closed.

I had to remove the fuse to stop this, which of course also disabled the central locking system. During a dry spell I removed and tested the lock mechanism, both micro switches functioned correctly. Inside the cast metal housing is a circuit board which contains a timer circuit which is intended to turn off the motor after I believe ten seconds. When I removed the cover I found the board had developed tin whiskers.

The lock was reinstalled and we manually locked and unlocked the car until I could get a replacement from a breaker. It took a couple of months to find a replacement in the UK and return to normal functioning.

How to remove and replace the lock is covered at the following URL,

Mercedes-Benz W124 Hatch Lock and Latch Replacement | 1986-1995 E-Class | Pelican Parts DIY Maintenance Article

Please note however:

If you are removing the lock you do not need to also remove the vacuum servo, simply disconnect the three actuation rods, the two electrical connectors and undo the bolts.

The difficult part is actually removing the lock assembly from the tailgate as it proves to be something of a monkey puzzle.

The trick is to sit on the load area with the tailgate down and resting on your knees, pull lock towards you, this removes the lock barrel from the tailgate. You then tilt the top of the lock assembly away from you, this allows the lower part of the lock assembly to clear the return on the bottom of the tailgate.

If replacing the lock with a different assembly, two 8mm bolts hold the lock barrel in place, simply undo and swap barrels with the original lock and you can carry on using the original key.

Replacement as the book of lies directs is the reverse of removal.

When removing and replacing the tailgate trim it does prove helpful to have another pair of hands to assist you.

One final point which may help, according to the circuit diagram one of the micro switches controls lock function the other controlling the interior lights on the D pillar.

A possible partial check on switch problems is to set the dashboard switch to lights on when tailgate is open and check if the lights illuminate with the tailgate closed. This might suggest gummed up switch operating arms.
 

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  • Tailgate Wiring 3331.pdf
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  • 72-265 Wiring diagram.pdf
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  • 72-270 Micro switch Testing.pdf
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