SL550 trunk won't stay open
 

We have a 2014 SL550 and the last two time the car was used I noticed the trunk lid closes just a few seconds after it reaches the open position. Probably wouldn't have noticed if there wasn't a battery tender hooked up in the trunk. It will close on me before I can get the pigtail connected/disconnected. We've never had the issue before and wondering if anyone has encountered this and may know what causes it.

It is likely the cold temps outside. When it is very cold, or freezing outside the gas in the struts do not work as well which causes your trunk to drift down and close. I bet it doesn't slam shut, but slowly closes huh? Depending on the miles on your whip they (the struts) could be due for replacement. Although I have heard many say that milage replacement scenario in the past I would always think about our GLK with 125k on it now. Our GLK hatch still remains open as it should in winter or freezing temps outside, so I always wink when someone mentions miles. Trust me my wife is in and out of that hatch numerous times daily due to her work and it is still going strong..

The struts do not cost much and in fact I just ordered some, but decided to send them back when they arrive tomorrow. Each winter my trunk does the same closing thing that you mentioned and each winter I say I am going t replace those struts. Eventually when the temps warm back up a bit, or spring arrives my hatch stays open like it should. Your call.

Best wishes..

Thanks for the response. The lid does lower slowly and when it gets to my back stops moving until I get out of the way. It has been below freezing for the high the last ten days and is timely for the issue. Also, the garage is not heated.

Did this a few weeks ago when temps dropped a bit. Bought on Amazon (Stabilius, same part as OEM), took 10 minutes with a flat blade screwdriver and a broom handle. Way better! Car is asleep for the winter now!

Yep! Also these..

I replaced mine with the Stabilus last winter and last week when the temps dropped here, the trunk dropped just like before. Not sure if I just got a bad set or if something else is the cause.

I had this happen with my 2016 as it was nearing the end of its warranty period. I took it to my local dealer and waited in their lounge while it was evaluated. The service advisor came out to see me after about 15 minutes and told me they wanted to hook my car up to their diagnostic (Star?) system to see if the trunk was “throwing any codes”. Asked me to approve this at a cost of $130. I immediately gave my consent to ‘do whatever is necessary to fix it at any cost’. I then said that I was assuming MB would cover this as the car was still under warranty, to which my SA said she didn’t realize it was a warranty claim. Unbelievable.

Thanks for the responses. We had a couple days where it warmed up a bit and the trunk did not creep down as quickly, so I'm going to assume at tbis point it is temperature related. We have detailed the car, put the battery tender on it, put Stabil in the gas, and covered it in the garage for the Winter. I'll see if the issue still exists next Spring when it warms up and change out the struts if needed.