I don't know any owner but Steve (MBenzNL - Home) reported some time ago about this and some other features retrofitted to an older W221. He did not explain which parts were necessary but the full retrofit needs new mirror glasses and wiring at least, I don't know if SW and version coding is sufficient for the existing Distronic Plus parts.

 

I have an 07 S600 and believe these cars came fully optioned and mine doesn't have this feature. However, driving it around for a while now and with the mirrors adjusted properly I don't feel there are large or any blindspots, but that's me.

Good luck,

J

 

I agree even if the mirrors are not big, perhaps the name "Blind spot assist" isn't perfect. But there is always a chance the driver does not observe a car next to it even if it actually was visible in the mirror. It could be something distracting the view, something else that needs to be followed etc. Then the assistance systems help.

 

My car came from the factory in Germany so things might be different. In my case Blind Spot Assist was an optional extra that required Distronic Plus. I do not remember the option code sorry.
At first I thought I had blind spot assist because of the way Distronic Plus was described, but after I took delivery to my dismay I discovered it was not there. My dealer explained the technicality.

 

What model year is your car? I misunderstood the original post, was reading too quickly I guess or guessing half of the question. If the OP is referring to a US 2007 MY car, blind spot assist was not available at the time, did not come along with distronic plus then of course.

Blind spot assist only came as an option later, the option code is 234 but it usually comes for free for car with Distronic plus (option code 233). I believe blind spot assist came with cars built some time starting from 3Q 2007.

 

I think by US standards my car would be a US 2008 MY car in which case I also read the post to quickly. That said, my car was spec'd in Germany and I definitely did not get Blind Spot Assist. I will get my vin number and check online again, but I am sure I would have noticed the triangles.