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Pneumatic / vacuum central door locking: advantages?

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sanchezc's picture
Highlands, NJ
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Anyone knows if they are they that, contrary to electrical systems, pneumatic / vacuum central door locking works:
* even if the battery is dead?
* even if the car is flooded / submerged, i.e. the electrical system shorted?
* and / or else?

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1999 E430
Re: Pneumatic / vacuum central door locking: advantages?

To me the only real advantage was how quiet it was.

Regardless of any advantages, it is going away due to the slowness of operation. Systems like Keyless Go require instant response, therefore M-B has been shifting to electric locks. Initially they added separate unlock solenoids, but I believe they have since gone completely electric (W203, W211, etc.).

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Re: Pneumatic / vacuum central door locking: advantages?

Based on what little I know about the different systems, I would expect that the pnuematic locks would open or lock as long as the vacuum storage canister has enough vacuum. That would be a pretty low depth not achievable unlerss the car is pushed overboard while at sea.

The electric door locks I am familiar with are different from the traditional Mercedes vacuum locks in that the key only opens the door you use it on. All others are controlled by a switch/s inside the car.

Maybe Vince can tell us how the newer Mercedes system operates. Is it the same as the systems on many U.S. cars or is it similar to the vacuum system?

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vince's picture
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Re: Pneumatic / vacuum central door locking: advantages?

I can't speak for the latest locking systems other than what I know from cars I own (MY2000 is the latest) and from what I have learned by studying various technical documents put out by M-B.

About the time the Smart Key came out -1998 I think, the locking system could be programmed to either a) unlock only the drivers door or b) open all the doors and trunk from the key. Depending on the program chosen, from the inside, when the driver's door is opened a) only that door unlocks or b) all the doors and trunk unlock. There is also a redundant lock/unlock switch on the dash or drivers door. The "power" to operate the locks comes from the PSE Module (vacuum pump).

The Keyless Go system complicates matters in that it requires instantaneous response so that when an authorized person (someone with the key card or Smart Key) touches the door handle, the system unlocks the car and wakes up the CAN bus. A vacuum system is too slow so initially M-B added electric solenoids to the existing vacuum system for unlocking only. I am pretty sure that the W203 and W211 systems have electric locks exclusively; undoubtedly the evolution of the Smart Key/Keyless Go/ CAN, etc. is driving the changes.

BTW, I discovered a lot of this by reading STAR Tuned Magazine, the free publication available on the M-B Wholesale Parts website. Anyone considering ownership of a post 2000 Mercedes or interested in the whys and wherefores of the changes we see Mercedes making should check this frequently (hint, hint STAR editors).

https://www.mbwholesaleparts.com/StarTuned/html/index.html

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