ML 500 mz

Was having a problem with liftgate not colsing, i.e., Hatch door lock (bottom of rear tailgate) was stuck in locked position and tailgate won't close (lock). I was able to get the lock to the open position, using a screw driver, and was in the process of removing door trim to access actuator. Well, the liftgate closed and now I can't get it open. Any way to open the liftgate manually?

Maj. Dundee

Now you have to remove the interior tailgate panel. Refer to the below link for removal instructions.

https://mbworld.org/forums/4941206-post5.html

ML 500 mz

Well... purchased actuator/handle assembly from Mercedes. According to vin#, part #A 163 740 07 93 is correct assembly for my '03 ML 500. Installed this morning..... doesn't work. Anybody have any history with this part? Maybe needs to be programed?

Thanks,

DrX

Check the tailgate unlock relay k15 in the engine bay fuse/relay box. Replace if necessary.

ML 500 mz

Thanks for the info, already checked relay K15. Swapped with another that I know works, didn't help. There's a central locking relay too. Didn't check that one, that might have something to do with my problem??? I'll check it today.

DrX

What exactly do you mean by "doesn't work"? Does it open and close? Can you unlock it manually, using the inside handle switch?

If the other doors lock, then the CL relay k20 is OK.

ML 500 mz

The tailgate will open manually using outside handle & it will close shut. It will not lock using remote or centeral lock switch. Other doors will lock / unlock using either centeral lock or remote. No sound (actuator cycling) is coming from tailgate. It's like it is not connected, yes.... it is installed correctly and the two wires are pluged into correct cennections.
I wonder if the system may have to be resynchronized with new actuator?
Didn't have a chance to check centeral lock relay..... I thought a relay isn't like a fuse, a fuse is good or bad, no gray area. A relay doesn't work that way.

Thanks...

DrX

Time to study the wiring diagram -> wiring-diagram-central-locking-cl-.pdf

Your doors lock, so relay k20 is good. That same relay locks the tailgate - no sound or movement there during locking means you have an open circuit in the tailgate lock actuator circuit. It only takes one break to cause this, anywhere between F1, X18/1, M14/7, and back through X18/1 to F1 and relay k15. The most likely places are the moving parts - k15 (which you haven't clearly established is good) and where the wires pass between the roof and the tailgate. Repeated wear could rub through the insulation or cause breakage. A corroded connector is less likely.

ML 500 mz

Thanks.....

ML 500 mz

I went to two auto parts stores last evening for K15 relay, neither had the correct item. Going to MB dealer today for relay.

Note: During this episode with tailgate, I've had the cargo compartment lamp shut off because auotmatic control feature stopped working, lamp would stay on continuously. I switched back to auto control position last evening, to check if that feature is operating since replacing actuator/handle assembly. It isn't, lamp remains on & is not switched on & off by opening or closing the liftgate.

Thanks...

DrX

You have a fault with the tailgate rotary tumbler switch/circuit, that tells the AAM that the tailgate is closed. It's labelled S88/1 in the wiring diagram and for your model I think it's part of the lock assembly p/n 163 740 02 35. The connector has brown & white wires - if you short out the connector, that should turn off the lamp. Then you need to replace the lock.

If you ground the grey wire from the handle assembly, you can test that the actuator is working.

ML 500 mz

Thanks for your help. Seems like the lock assembly may have been the problem all along. I'll check it as you suggest asap (probably this weekend). I'll let you know the results.

Thanks again...

ML 500 mz

Well... "shorted out" the lock assembly & the lamp went out. So, looks like that is the problem. I guess the lock assembly being bad would cause the actuator not to operate?
The story of my life... I always start replacing the hardest to get to and most expensive part, if that doesn't correct the problem, work down from there.

Thank you....

DrX

Applying Occam's razor, you only need to replace the lock assembly. The tailgate actuator can't lock it because it's not properly closed. That would explain the lack of sound on locking. You can assume that relay k15 and the circuit is OK for now.

In hindsight, your initial description was that of a faulty lock.

ML 500 mz

I'll order lock assembly today, and keep you posted.
Your knowlege & advice is appreciated.... Thank you