My ML320 central locking system seems to work.... except for the rear door. It does not lock. I checked fuses - all seemed fine. I could feel the 2 relays in the fuse box clicking when I lock and unlock. When I lock I do not get the 1 time blinking of the lights. Had some trouble with the rear door mechanical mechanism not long ago... not sure what it was but it seemed to be locked in the closed position, when I tried to close the door it was hitting the latch. Pried it open, it has worked since. Perhaps I broke something. Any ideas?
Thank in advance.
PS Europa has become a SAAB dealership. (I live in Santa Fe)

The lock solenoid in the tailgate latch is prone to breakage. If it breaks, the microswitch doesn't close and the anti-theft system "thinks" that the tailgate didn't lock. That's why you don't get the blinking light. The inner tailgate panel needs to be removed for examination of the latch and lock.
Gilly

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Gilly, If I remove the panel would the fix be obvious? or is this a job for a service tech. (obvious to me a novice at fixing things lol)

Getting the inner panel off would be kind of tricky, you may be better off letting someone with experience do it. You almost have to replace the locking solenoid, not a reliable fix available.
When the solenoid fails, you'll notice that the small lever inside the tailgate actually will lock and unlock the tailgate. But the solenoid will only work in one position, can't remember which way is push and which way is pull. I think it will unlock it, but it won't lock it when which plunger breaks off, could be just the opposite, you should be able to figure it out.
Gilly

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Gilly, do the other newer chassis have the same kind of power locks too?

Kuan

Kuan:
I'm not sure what you mean by "other newer chassis". The 163's all use the solenoid locking system, which is unique for Mercedes.
Most models use vacuum, except for the 203 chassis C class, which uses an electric motor scheme, but not a solenoid set-up.
The new Keyless-Go cars have vacuum at all doors, but also have a "fast acting" unlocking system for the door which is being opened via Keyless-Go, but I haven't been schooled in this system yet and am unsure how this "fast acting" unlocking is actuated.
Gilly

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Thanks Gilly, I guess I should have been more specific. I was thinking about the 203, 210, 220. I was wondering why MB would go with a whole new central locking system when they've used the vacuum system for such a long time and after it had worked so well.

Kuan

Kuan:
I think to a certain extent, some of the changes were made to the design philosophy of the ML to keep the price competitive with other vehicles in it's class. The ML I believe was undergoing alot of it's engineering studies at the time that the company knew it had to stop "damning the expense" because if things went on as they were for much longer, they were going to drive themselves right out of business. Now, too a certain extent, I think they may have swung too far the other way. Things have been inproving somewhat, especially in terms of interior component material, everything is much nicer now, and especially in 2002 with the climate control and window switch unit.
The central locking system had a few problems at first, most notably bad microswitches in the door latches and also the previously mentioned breaking lock solenoid in the tailgate.
Gilly

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