Good evening All. First off I want to continue to give a shout out to all the great folks on here.. Y'all have been a great resource for me with this SL500. 2003, trunk is being stubborn. If I slam it too hard then the left "ear" falls down a little bit then top won't drop. What is the common culprit for these cars to continue to say Boot Not Shut even though it is? Is it a dirt contact electrically back there?
Thanks in advance

Jim

 

The trunk has two latches that must be closed for the top to function. The first is the one that should close when you lightly close the trunk, the second is the one that the soft close pulls it to. If you slam the trunk hard, you can bypass the soft close and get the second latch to close. However, this is hard on the latch and can crack the 3rd brake light. You need to fix the soft close so that it works as designed.

In addition, you should not be able to knock a flap out of position that easily. It either needs to be adjusted, or you need to replace the gear backing plates with the revised versions.

 

First to know is the R230 trunk lid has a soft close function which avoids the need to slam it. Pressing gently on the lid engages the latch with the first click and starts the soft close which engages the second click. It’s this which makes the car recognise the lid is closed.

If you are having to slam the lid closed, it’s a sign the soft close is broken. If other pneumatic functions are working, it’s likely the latch is the trunk lid is leaking air and needs to be replaced or repaired, if possible.

The pneumatic pump in the trunk shuts down this function if a leak or other problem is detected. It’s a very common problem and the first thing to try is removing the yellow 20A fuse in the fuse area under the storage boxes and replacing it. This erases the pump memory so that it will re-enable the soft close.

There are lots of other threads describing this problem.

 

After a few sealing attempts on the pull down assembly my trunk closes most of the time but will fail on a rare occasion. I could pull the fuse fairly easily but to make it even easier I added an 11 inch fuse extender and routed it up to the storage bin for easy access.
A better fix will be replacing the unit, but still recovering from $5000 in roof cylinder rebuilds so it will wait a little longer.

 

Yes, a fuse extension cable makes it easier to power cycle the PSE pump. The pneumatic latch seems to suffer unduly from the heat in the US, here in the UK, it’s dampness in the trunk which gets you. $5000 on cylinder rebuilds! 😳 That’s a delight waiting for me around the corner.

 

What other pneumatic functions are there, so I can see that this basic function is or is not the problem?

On a 2003 SL, would this be the door lock buttons on the top door sill?

Greg

 

Yes, the door locks are pneumatically controlled, so too is the fuel filler cap lock and the lock to the storage bins behind the seats. If you have massaging seats, they are powered off the same pump which is in the trunk on the left hand side underneath the pump which runs the roof.

If the door buttons are going up and down as you lock and unlock the car, the pump is working. There’s a set of valves which determine which devices are activated.

 

For some reason, known only to Mercedes engineers, they also chose to have the least reliable module in the car (PSE) be the module that reads the trunk divider switch. If your PSE fuse is blown, the top will not work and you will get a message to close the trunk separator even when it is actually closed. Not content with that, they put it at the very bottom of the trunk, so that any water leakage into the trunk will destroy it. Then, fearful that the water might drain out before it was damaged, they surrounded it with two large sponges. Finally, after discovering that some pumps were still surviving, they designed a trunk latch that is guaranteed to fail after a few years and work any surviving pumps to death.

In their defense, when the locks are working, they are very quiet and dealers will replace the pesky pump for a mere $2500 when it does inevitably fail.

 

It’s a dreadful design isn’t it? What’s absolutely essential is to keep the trunk dry and the C pillar drain holes clear so that water draining off the roof has some place to go other than inside the trunk.

I’ve recently been treating the rubber seals with WD-40 with silicone which is cleaning and softening them so they seal better.

 

Thank you all for some great responses on this. So I did confirm the soft close isn't working. I read that there is a 20amp fuse I need to check. When you say storage boxes, are you talking about the storage behind the seats? The drivers storage has a cd changer in it. Or are we talking about something else? If you could please explain. And if it is under that storage how do you get to it?

Thanks

Jim

 

I’m sorry, I am in the UK and was not sure if the bins are swapped around for the US. Since the CD changer in on your drivers side, they are not, so the fuses you are interested in are underneath the bin on your passengers side.

You can remove the floor of the bin by very gently pulling back on the tabs which are at the back of the bin and lifting. Be careful, if you overdo it, you will break the tabs.

You can then reach in and push the vertical trim plate at the front out from behind. You’ll then see the fuses, the one you want is yellow, 20A, about 3 or 4 over from the left. If the fuse is blown, replace it with a new one, otherwise just plug the fuse back in. You should hear the PSE pump in the trunk run for a short while. You can then check the individual functions, central locking, trunk lid soft close, massaging seats if you have them.

If the pump runs on after the soft close, you may well have a leaky valve. If nothing works, it’s likely the pump has failed, it uses a graphite rotor which is quite fragile.

Good luck, let us know how you get on.

 

It was right where you said it would be BlueSL. So the fuse was intact, I removed it and plugged it back in. Now the trunk does a soft close.and then I hear air for 6-8 seconds then it stopped. Trunk held tight. Does this sound correct to you? is there anything else I need to check or am I good to go? Great info, thank you very much

Jim

 

You are good for about 3 cycles and then it will shut down the pump again to prevent overheating. You need to fix the leaks in the trunk actuator or replace it.

 

If you are hearing air escaping, that does suggest a leaking valve. Normally the pump runs on for a couple of seconds to top up the pneumatic reservoir. It will tolerate a leak for a few times but will eventually shut down that function to protect itself from extended running. See how it goes, if the soft close stops working, it’s for that reason and you can restore it by power cycling the fuse.

Above all, keep the trunk dry by clearing the C-pillar drain holes.

 

Great info, Thanks! I will look for that air leak back there. If I may, I would like to take this time to ask two more questions instead of starting a new thread. Where should I start looking when the cigarette lighter port doesn't work, would I look under that passenger storage compartment? maybe blown fuse? Second, what do I use to remove this sticky substance that is on the hazard/lock/unlock button on the dash? I can't imagine mine is the only car that has done this.

Thanks!

Jim

 

I’ll check where the fuse to the cigarette lighter is but if you have - or can borrow - a voltmeter, you can check whether there is 12v between the centre pin and the metal surround. Power to this socket comes from the trunk battery and is interrupted if you have the consumers offline message. Plugs you insert into it should have their own fuses which are often not replaceable so it’s a good idea to check with multiple devices and the voltmeter.

That socket is far from ideal of course in the way it works but just like USB-A in phone chargers, it’s become a sort of standard which is now difficult to change.

The sticky controls are not just down to your car, or the R230 but a whole generation of cars where the controls and other items you touch were coated to provide a sort of soft touch feel which unfortunately deteriorates from oils in the skin, sunlight and just existing!

The problem is replacement parts, even if they are available, were made years ago and are likely also deteriorating in storage. You may get an improvement by wiping the surface down with an alcoholic wipe but it’s not a permanent solution. Don’t be tempted to use a strong solvent like benzene or acetone or paint thinner because they will attack the brittle plastic underneath and really spoil your day.

There are companies who can remove the finish and replace with Matt black acrylic and I have used one in the US called StickyNoMore. You remove the trim parts, switches, air vents, do as much disassembly as you can, take a deep breath and courier your precious parts over to them and they come back looking like new. I refurbished the parts from a Ferrari F355 and they did an excellent job. They are not cheap but in the context of nowhere else to go, they’re a lifeline. There may be other companies doing the same thing but I have not used them.

 

OK, according to a chart I have, the fuse feeding the cigarette lighter is f11 in the fuse box at the back of the engine bay on the drivers side. It’s a 30A fuse, should be green. Make sure to fit the lid back securely to prevent the ingress of dirt and damp.

 

Thanks again BlueSL. So the 30a fuse is good. Any other thoughts what could be the issue of the port not having any power? Or could the cigarette lighter port itself be bad?

Also how do the hazard, lock and unlock buttons come out of the dash? Do they just pop out or do I need to get behind the dash? Thanks again for the tip, I plan to get them refinished.

Jim

 

The problem could be with the wiring to the socket, the socket itself, the plug and cable or the device.

Have you verified there is +12v at the centre pin at the back and continuity between the outer shell and ground? Better to do this basic test before you go further.

Are all the other electrical consumers working? If you see the message “consumers offline”, power to the connector is interrupted.

 

Good morning. So I did the DIY and put the epoxy over the bb ball bearing areas on the soft close mechanism. So I confirmed I fixed the air leak. I have opened and closed the trunk 4-5 times and it pulls down every time. So now I am facing another issue. When I go to drop the top it still says boot not shut but this time not in red, just the standard grey. Any idea how I can fix that? Also when I go to open the trunk after it has been pulled down it makes a slight pop and lifts up, is there a chance it is too tight now or is it supposed to be very snug like that? I feel like I am so close to getting this, almost there guys. Any words of wisdom would be very much appreciated.

Thank you all for your time

Jim

 

Is the red light still on at the driver door trunk release button after it pulls down? It is probably adjusted too tight to completely latch. The mechanism is mounted on slots, so when you remove and replace it, you can change the adjustment.

If the light stays on when you close it, try rotating the latch pawl one notch with the trunk open. It should rotate closed (soft close feature) and the light should go out. This would indicate proper function, too tight of adjustment.

 

Thanks for the info. I am a bit confused though. Yes the red light is on at the trunk release button on the door. So you say to rotate the latch pawl one notch. How do you adjust it? And are you saying just by rotating it the light will go out, or rotate it then close it again then the light will go out once it closes correctly? Also the fixed latch at the base of the trunk I see also has an adjustment, do I mess with this? If you could please help me understand how to adjust this latch pawl I could start there.

Thanks again for the info! Much appreciated.

Jim

 

To test soft close, with the trunk open, move the lock pawl forward until it clicks. This should kick in the soft close, rotating the lock pawl further closed, and the light on the trunk release should go out.

Assuming that it was properly adjusted, the one thing that you 'messed' with was the position of the latch in the slots. You should be able to see where the screws were and put it back the same place. If not, try it a little bit forward or a little bit back. Close the trunk and see if the light on the trunk release goes out. You can also adjust the catch if necessary, but since you had the latch off, I would start there.

 

Good morning. When I reassembled the mechanism I put the screw heads back exactly the way they came off so the latch wouldn't be out of alignment. I do think it is closing too tight, because when I open it it "pops" a bit. So with the trunk open I click the pawl to engage soft close, but the red light on the door stays on. You had mentioned the mechanism is mounted on slots and can be adjusted. What did you mean by that? At this point should I adjust the catch a little to loosen it up? Sorry, I am just not following you on your explanation. Sorry about that. Thank you very much for the continued guidance.

Jim

 

If the red light stays on when you close the latch with the trunk open, you have an issue with the micro switch, wiring, or a module. There are two switches under the round, black release servo. Start by checking them and the wiring to them. One reads the initial click/safety latch, the other the final, full lockdown. Both have to be recognized for the roof to function.