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Old 05-13-2013, 12:03 PM
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Is infrared locking centrally controlled

I've got a '92 300SD, W140. The trunk lock has never worked as the key slot is corroded. As I generally use the remote Infrared to lock the car, this is not a problem and I have never wanted to unlock it with the key. However, the locking cylinder is coming apart and I would like to replace the locking mechanism. I don't care if the key works or not, but I do want to be able to unlock the car with the trunk IR sensor.

The question is, "is the IR ID embedded in each of the (trunk and door) sensors, or is it controlled somewhere centrally?" Put another way, does the IR sensor need to be rekeyed as the physical key does? I'm perfectly happy to put in a locking unit for which the physical key does not work, but I do want the IR to work, so I propose picking up a used unit if I don't need to worry about the IR.

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Old 05-13-2013, 07:45 PM
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Central module, I believe it is called the IR module on this year, I would need to double-check. At any rate, yes if you need the IR sensor it can simply be ordered, not special to a particular chassis. (or from a used parts place).
The IR sensor is seperate from the latch and key stuff though, it is the small red/green window on the trim strip below the trunk on the earlier models like this. At least I think it has the red/green windows, it might just be a black window. Possibly you are mis-aiming the key, this is done line of sight on IR systems.
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Old 05-14-2013, 11:26 AM
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Infrared sensor on w140

Thanks for the feedback, Gilly. The locking mechanism I have now works with the IR (a black window to the left of the keyhole). The trunk also opens by pushing the button, but the button does not return. The chrome cap on the key mechanism has ceased to function in protecting the plunger into which the key fits and the spring which pushes the plunger back out after you have opened the truck is toast, as well as the tumbler. So, I can get a used one to replace this one and maintain the IR function while tightening up that whole area against corrosion.
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Old 05-14-2013, 11:57 AM
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Central unit. Under the back seat, IIRC. Does your car have the switch on the dash to open the trunk? Does it work? (Press and hold for a couple of seconds.)

Jim
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1995 S350D, Green with black leather interior.
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Old 05-20-2013, 01:29 PM
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Further question on w140 trunk lock

Quote:
Originally Posted by Jadavis View Post
Central unit. Under the back seat, IIRC. Does your car have the switch on the dash to open the trunk? Does it work? (Press and hold for a couple of seconds.)

Jim
Thanks, Jim. I don't have a switch on the dash. I cannot open the trunk remotely, i.e., cause it to open up. I can unlock it remotely with the IR key.

However, I do have a further question. Did MB change the IR operation between '92 and '95, i.e., can I install a '95 w140 lock and expect the IR to work? I can get a w140 lock from a '95 model but want to assure that MB did not change the IR operation. Seems like I read somewhere that they changed it in some way, but it may have been later than '95.

bTW, I may be wrong, but I think the unit under the back seat is the vacuum distribution (and perhaps pump) for various things, like the lumbar support and the trunk lock. I suspect the IR unit is in the computer box, but, now that I think of it, it may be integrated with the vacuum pump.
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Old 05-20-2013, 02:39 PM
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It's been a couple of years since I was under the back seat, so I could be wrong. Try finding out the part numbers for the module in both model years. If it is the same, it should work.

Jim

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