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Discussion Starter #1
Hi, wonder if someone can help please?
My boot won't lock at all. I'm pretty sure it did when I first got the car 18 months ago but can't be 100% certain.
When I've locked the car with fob, doors are locked but boot will still open and activates the alarm. I tried locking it with key but key won't turn, so I sprayed inside with WD40 in case it's just seized up, still won't turn.

I'm wondering if I have the right key, whether the lock has been changed at some point.
Or, could the boot lock have just been deactivated and can it be reset somehow?

Thanks for any advice
 

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Super Moderator CA 2012 SLK55 AMG w/P30
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11,984 Posts
NEVER use wd40 on locks or electronics. It is not a lubricant, rather a solvent. The carrier drys and more dirt and dust will accumulate in there.

Others may say to use it on locks but not IMO and many others.
 

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Super Moderator CA 2012 SLK55 AMG w/P30
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11,984 Posts
One guaranteed method is disassembly


Can try spraying graphite powder but after you've already sprayed wd40 in there, it would seem you would need to either keep trying (GENTLY) to keep turning the key. The primary cause of that issue is always using the fob. Like most things mechanical, regular "exercise" is needed to keep it functioning, as well as the occasional lube with graphite. Graphite is old school but there are newer products available.

No graphite? Got a pencil? Rub the lead up and down the key grooves and then insert and again, turn it gently back and forth.

It may eventually start to rotate but always, gentle/do not force it.
 

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Registered 2002 SLK320
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1,778 Posts
One guaranteed method is disassembly
And that is the best way on MB Locks, use a little synthetic grease to reassemble it, and get in the habit of using, (exercising) the Lock Barrels with the Key Blade at least once a month ;)

I don't think you can deactivate the boot lock BTW.
Agreed, I've never seen that option / function on R170 ;)

HTH,
 

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Super Moderator UK SLK 55 AMG 2007
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25,574 Posts
Seized lock mean lots of key wiggling. And repeat, and repeat.
Takes ages.

Just for fun, try a battery reset.

Disconnect battery for at least 30mins.
Reset clocks, resync windows and try remote lock.

Still no joy?
Check out pse for signs of water. (lots of PSE diy threads to assist in 170 diys).

One more thought on the lock mechanism.
For what ever reason, it may not be the original lock.
Also, the lever you use to manually open the boot can also get gunked up and stick.
Make sure it is dropping back into place. (you can assist this but it is awkward to see what you are doing).
 

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Premium Member 2001 SLK200K/2001 SLK320
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1,497 Posts
On the post fl, the lock turns a nylon or plastic cam which then moves a sleeved rod to lock or unlock, it is this cam and rod that needs the lubrication. Access is via the plastic shield in the boot. Open the boot, sit half inside half outside, remove the shield that's now in front of your head and all will be revealed .. dunno about the pre fl because I haven't got one :)
 

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Registered 2001 SLK320
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878 Posts
Lots of discussion re the lock cylinder itself but the trunk should lock with the doors when locked from the fob.
That suggests the actuator is also part of the issue. M4rCu5 hints at this but not directly.
The PN is A1707500284 and available used on eBay for under $30.
 

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Premium Member 2001 SLK200K/2001 SLK320
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1,497 Posts
Aye, I forgot to mention that there's a spring in there as well that also gets gunged up. Inspection and disassembly/clean/regrease is probs the way to go
 

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Registered 2002 SLK320
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1,778 Posts
Yeah, I missed that, just re read OP, I think it is the end bit where he says he may have the wrong key, (which obviously he doesn't) that kinda muddies the waters ;)
 

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Registered 2004 SLK320
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10 Posts
On the post fl, the lock turns a nylon or plastic cam which then moves a sleeved rod to lock or unlock, it is this cam and rod that needs the lubrication. Access is via the plastic shield in the boot. Open the boot, sit half inside half outside, remove the shield that's now in front of your head and all will be revealed .. dunno about the pre fl because I haven't got one :)
I had this problem when we first got our 2004 SLK320. You could hear the actuator trying to lock the trunk when you locked the doors but it wouldn't work. Pulled the plastic cover and watched the action. Figured it to be two problems. It needed lube as mentioned above, plus the in trunk safety release cable was hitting the mechanism just enough to bind it up. Rerouted the cable to where it should be and a little Tri-Flow on the mechanism and it has worked just fine. It is loud enough I can hear it actuate in the driver's seat when it auto locks at 8 mph. Till I realised what the noise was, I thought I had something loose in the trunk that was clunking on takeoff!
 
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