85 300SD: trunk won't unlock!

The key still appears to work OK. You cant push the button in and the key turns like always; you see all the other locks pop up, and you hear a "click" inside the trunk as if the vacuum actuator has moved.
But the trunk remains closed, won't open! Yea, it is a clunker now, but I'd rather not take a crowbar to it. I suppose the only other thing to do is to pay big $$$$ to a locksmith? I got it...take the rear seat and gas tank out? ;-)
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Your alarm system is armed. When it is armed, a bar goes across the lock so you cannot push it.
Remove the rear seat bottom. Look at the left, drivers side area for a loop attached to thin cable. It may be under the sound deadener. You will need a 2nd person to pull the cable while you push the trunk button.
If you don't want to fix the alarm problem, remove the bar from the trunk lock.....

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WHAT alarm system? I wrote: "You cant push the button in and the key turns like always...." That was a typo....you CAN push the lock button in OK! At least it feels like it is moving inward a normal amount. Sorry for confusion.
Regards, Jim

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Be sure you're using the Master key. If the Master (square) key was used to manually lock the trunk, then only the Master key will unlock it. The same goes for the glove compartment.
These cars came with two different keys, a Master key and a Valet key. The Master key was used for storing valuables in the glove compartment and trunk, so that giving the Valet key to a parking attendant would keep the valuables from being accessed. If the trunk was manually locked with the Master key, then the interior trunk release switch won't release the trunk, nor will the trunk unlock with the other doors on the car when using the central locking system.
If I remember correctly, the Master key is square, and the Valet key is oval. If you're not using the original MB keys, try manually unlocking the trunk using a different set of keys than you have been trying.

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Still got all your books in the car? Get out the maintenance booklet and see if you still have the data card glued to the inside back cover. Go down the list of 3 digit numbers and tell me if you have 551. 551 is factory alarm.

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We are using the same square key, the ignition key, and the same procedure that has ALWAYS worked before to unlock the trunk. I took the rear seat out and sure enough, there is solid steel behind, no way to get into the trunk. This was useful anyway, as the gas gauuge is intermittent, and so I cleaned and reseated the level tranmsitter while the seat was out. I finally had no choice but to force the trunk lid up. After leverering it to the side of the lock, it was up far enough that I could loosen the two 10 mm bolts holding the latch onto the trunk lid. I removed the other latch to the left that has a round hole, to see if that was causing the problem, but it wasn't. Some of the black plastic around the lock broke, but after getting it opened, the lock mechanism still works the same, and does unlock the doors fine, but there is still the same unlocking problem. It is stuck again after unlocking everything. . And yes, it is the master key, I have no valet key. But at least now when it is stuck and won't unlock, I can easily get it opened with a 10 mm wrench. (problem is we can't put anything of value in there now, since a thief could also get it opened the same way) Also there is about a 1 inch or so gap between trunk lid and body, so water can get in. Oh well, it is a clunker like I said, will probably replace it within a year.
There was no such arming wire for an alarm, there is no device up front for arming/disarming an alarm....and the former owner would have instructed me on the alarm system if it had one. Thanks, Jim

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Pmail me your vin number.

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My friend, you pried your trunk open and it is the beginning of fall. Soon you are going to have a trunk full of water. Did you even call a locksmith to see how much he might charge you for opening the trunk without destroying the function of your trunk.
It would have been a whole lot cheaper to have a locksmith drill open your lock (Probably less than $50) than to destroy your trunk. Then the only thing that would be needed to do is to replace the lock. By taking a crow bar to your trunk you probably hashed the lid and the sealing rim of the trunk.
You would have done a whole lot less damage cutting an 8 inch hole in the bottom of the trunk and reaching up to fix it. At least that could have been fixed when you were done.
--

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Roger Shoaf

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