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Had the "trunk wont close in the cold issue".
My guess is that the motor on the side probably gets weak over time, or friction increases in the unit and it wont pull the trunk down all the way when it is cold.
Been having the issue for two seasons now. Every time that happens its too cold to replace the trunk actuator. Then when it warms up I forget about it. Not this year.
Only downside is that I won't know if this worked until winter.
Takes about an hour or so to do. Not super difficult.
Need Torx bits, screwdriver and some tools to get the plastic pins out without breaking.
I use the silicone spray and contact cleaner when I put the stuff back together. Not needed but makes sure the connections are good.
Step 1 - Remove the plastic pins. There are about 12. Dont forget the ones in the sides
Step 2 - Carefully remove the whole backing area. Carefully because you want to unplug the lights and switches as you go. Don't tear off the wires.
Step 3 - Take the open/close switch out of the backing and plug it back in. You want to do that to be able to test the trunk and open/close it at the correct height
Step 4 - The tricky part. Get access to the lock. There is a black box thing on the left side. Press in the sides to get it out. Then use your key, unlock the manual lock. Loosen the bolt there, let the whole unit drop. This is where the open/close button helps to open the trunk to the correct height to get in there.
Step 5 - Unhook the part to the lock. This is how you manually unlock the trunk.
The unit will work without this cable plugged in, but then you cannot open the trunk with the key.
Step 6 - Unplug and replace the motorized unit. Only two torx screws holding it in. You can get them aftermarket for around $100. It might work or not.
OEM was $500, but it fits and works.
Step 7 - Put everything back and test..
Thats it. Be careful. Work slowly, don't break anything.
Last edited by waterzap99; Feb 9, 2025 at 10:25 AM.
Had the "trunk wont close in the cold issue".
My guess is that the motor on the side probably gets weak over time, or friction increases in the unit and it wont pull the trunk down all the way when it is cold.
Been having the issue for two seasons now. Every time that happens its too cold to replace the trunk actuator. Then when it warms up I forget about it. Not this year.
Only downside is that I won't know if this worked until winter.
Takes about an hour or so to do. Not super difficult.
Need Torx bits, screwdriver and some tools to get the plastic pins out without breaking.
I use the silicone spray and contact cleaner when I put the stuff back together. Not needed but makes sure the connections are good.
Step 2 - Carefully remove the whole backing area. Carefully because you want to unplug the lights and switches as you go. Don't tear off the wires.
Step 3 - Take the open/close switch out of the backing and plug it back in. You want to do that to be able to test the trunk and open/close it at the correct height
Step 4 - The tricky part. Get access to the lock. There is a black box thing on the left side. Press in the sides to get it out. Then use your key, unlock the manual lock. Loosen the bolt there, let the whole unit drop. This is where the open/close button helps to open the trunk to the correct height to get in there.
Step 5 - Unhook the part to the lock. This is how you manually unlock the trunk.
The unit will work without this cable plugged in, but then you cannot open the trunk with the key.
Step 6 - Unplug and replace the motorized unit. Only two torx screws holding it in. You can get them aftermarket for around $100. It might work or not.
OEM was $500, but it fits and works.
Had the "trunk wont close in the cold issue".
My guess is that the motor on the side probably gets weak over time, or friction increases in the unit and it wont pull the trunk down all the way when it is cold.
Been having the issue for two seasons now. Every time that happens its too cold to replace the trunk actuator. Then when it warms up I forget about it. Not this year.
Only downside is that I won't know if this worked until winter.
Takes about an hour or so to do. Not super difficult.
Need Torx bits, screwdriver and some tools to get the plastic pins out without breaking.
I use the silicone spray and contact cleaner when I put the stuff back together. Not needed but makes sure the connections are good.
Step 1 - Remove the plastic pins. There are about 12. Dont forget the ones in the sides
Step 2 - Carefully remove the whole backing area. Carefully because you want to unplug the lights and switches as you go. Don't tear off the wires.
Step 3 - Take the open/close switch out of the backing and plug it back in. You want to do that to be able to test the trunk and open/close it at the correct height
Step 4 - The tricky part. Get access to the lock. There is a black box thing on the left side. Press in the sides to get it out. Then use your key, unlock the manual lock. Loosen the bolt there, let the whole unit drop. This is where the open/close button helps to open the trunk to the correct height to get in there.
Step 5 - Unhook the part to the lock. This is how you manually unlock the trunk.
The unit will work without this cable plugged in, but then you cannot open the trunk with the key.
Step 6 - Unplug and replace the motorized unit. Only two torx screws holding it in. You can get them aftermarket for around $100. It might work or not.
OEM was $500, but it fits and works.
Step 7 - Put everything back and test..
Thats it. Be careful. Work slowly, don't break anything.
Thanks for your very nice writeup of the trunk actuator replacement. My 2018 S-class is having the same problem and I am thinking about doing a replacement DIY. Now that it has been a year, did the replacement of the trunk actuator solve your issue?
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