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Discussion Starter #1
So I've had this 66K miles 2005 SL500 for a year now and I love it! Everything works including roof, etc. Issues with it though is trunk lock and I was hoping someone has had same experience and gotten them resolved. Any help would be appreciated!

1: So trunk worked fine when I got the car. Everything from release with remote to emergency release button in trunk to release switch in car worked like they should.

2: After few months I could hear hissing from trunk lock. I read through forums and sealed all the ball bearings on actuator tight where I could see hairline cracks. Reset consumer battery and all was fine for a short while.

3: Next to was switch on drivers door. Bought new switch. Nothing. Just stopped working... Next was trunk release by remote. Just stopped working.

4: Now remote and switch on drivers door doesn't work, but can be opened with the key in fob. Decided to ignore issue till later as I had access to the trunk with key.

5: All of a sudden trunk pops open while driving...

6: I disconnected power lines from actuator mechanism in trunk to stop trunk from popping open while driving. Pneumatic works fine as pull down works consistently.

Consumer battery is new and works fine for all other systems. I trickle charge to full once every other week or if car is not driven for 2 or more days. No issue with battery just want to keep it healthy. Battery charge controller behind trunk lining near battery is good. Charge controller relays are also good. Pneumatic pump is fine as locks are good and I always keep seat bolster dials to '0' so no air leaks from pneumatic system on seat as they have usual leaking bolster inflator bags.

Any ideas anyone?
 

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I would get the error codes read with Star. Hopefully that will point you in the right direction.

Does remote work on passenger door? Fresh batteries in key fob and a sync will at least rule out issues with the remote.

Never heard of a lid pops open at speed. Sounds like the control unit is acting up.
 

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Although you sealed the ball bearings, you may have a leak on the diaphragm on the trunk lock. Mine actually started doing that first. BTW, to reset the PSE for the turnk lock, there is no need to disconnect the consumer battery - just pull the fuse for a minute. It's #71 on the rear panel.
 

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I've got no SL currently, however the 'popped open at highway speed' reminded me of the description in my W221 manual. The Emergency inside release (green button in my car) can be opened at any time, including while at speed. Perhaps there is something going on with that switch in your trunk?

Good luck with this, I recently went through the drama of having someone close my trunk while both batteries were disconnected. Only afterward did I find out the mechanical key lock was toast! I had to cut a hole in the spare wheel tub (plastic) and reseal it after reconnecting the consumer battery ground strap.
 

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I've got no SL currently, however the 'popped open at highway speed' reminded me of the description in my W221 manual. The Emergency inside release (green button in my car) can be opened at any time, including while at speed. Perhaps there is something going on with that switch in your trunk?
That's a good thought!

Good luck with this, I recently went through the drama of having someone close my trunk while both batteries were disconnected. Only afterward did I find out the mechanical key lock was toast! I had to cut a hole in the spare wheel tub (plastic) and reseal it after reconnecting the consumer battery ground strap.
The plastic on my trunk latch is deteriorating to the point that where the mechanical linkage from the handle connects, it is broken so that my manual unlock would not work either. I fixed it with some JB Weld and bailing wire, but not trusting it, I drilled a hole in the lid behind the tag so i could get a screwdriver in there and trip it if necessary.
 

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My GF's 2008 SL550 suddenly started giving her a trunk open warning. I could hear the dreaded hissing coming from the trunk latch and the draw down won't pull in. After removing the latch assy and still hooked to the vehicle PSE pump I noted the draw down piston would not push the latch fully closed. Inspection of the ball bearing fittings showed no cracking. I removed the entire latch and put some low pressure air to the latch assy and discovered air from the big draw down piston housing. I isolated that component by placing low pressure air right on the actuator and observing the hissing air escaping from the housing. I am assuming there is some sort of bladder inside the housing that has ruptured as there needs to be a lot of mechanical force to push the latch lever out and compress the return spring inside the piston housing. I have ordered a new latch assy. and it appears that this one has been replaced just a few years ago.
 

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Yes, there is a diaphragm in there. The tabs that hold the plastic housing together crack and allow air leaks. Some fix it with epoxy (like with the ball bearing). I fixed mine with zip ties:

 

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Discussion Starter #8
Does anyone have a wiring schematic of the R230 trunk lock system? Hopefully covering all components from driver's door release to emergency truck release and pneumatic (pull down) latch itself? Also, is there a separate control module for the trunk lock?

I have an icarsoft MBII... doesnt see a module. I also have the MB WIS/ASRA workshop discs but cant find a wiring diagram in it...

Any help would be greatly appreciated!
 

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Does anyone have a wiring schematic of the R230 trunk lock system? Hopefully covering all components from driver's door release to emergency truck release and pneumatic (pull down) latch itself? Also, is there a separate control module for the trunk lock?

I have an icarsoft MBII... doesnt see a module. I also have the MB WIS/ASRA workshop discs but cant find a wiring diagram in it...

Any help would be greatly appreciated!



Why can you not find the diagram in WIS?
 

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Consumer battery is new and works fine for all other systems. I trickle charge to full once every other week or if car is not driven for 2 or more days. No issue with battery just want to keep it healthy. Battery charge controller behind trunk lining near battery is good. Charge controller relays are also good. Pneumatic pump is fine as locks are good and I always keep seat bolster dials to '0' so no air leaks from pneumatic system on seat as they have usual leaking bolster inflator bags.

Any ideas anyone?
I really don't have a direct answer, although the answer that @ DLAFEVER posted is probably the most plausible one, but I just wanted to chime in on the need to trickle charge your consumer battery.

I have a SL550, and previously had an 05 SL500, and never had to trickle charge the battery, even after it going unused for 2 or more weeks. If the battery is in good condition (the battery in my SL500 was 4 years old when the car got wrecked), you shouldn't have to go to those extremes. If the battery looses enough charge over a 2 week period that the consumers don't come on line, then there's something wrong with it, or it's worn out, or you have something draining it.

Did you make any modifications to the MOST system? Replaced or added some devices? If that is the case, it's possible that your MOST system is not going to sleep properly, draining your battery. A short, or a lamp that's always on could do the same thing.

Bottom line, under normal circumstances, you shouldn't have to do any of those things with your consumer battery.
 

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As a followup, I installed the new latch assy and tested the system. Latch performs as expected and the draw down feature was restored. The problem was I still got a trunk open warning. I removed the latch and verified that the latch position switch continuity for both the open and closed positions were working. I jumpered pin 1 and 3 on the harness to verify the input to the logic circuit worked. Every time I re-installed the latch it would give the trunk open warning. Problem was the new latch came without the plastic socket end for the mechanical release rod. Even though I measured the old rod length before installing the end on the new latch the mechanical release would push back just enough to trigger the microswitch in the latch release. After much fiddling with the length on the release rod I finally hit the sweet spot.
 
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