But touch wood.... I remember when DPF's first became news...In my locality, Lady bought a VW Tiguan.. Lovely car, grand to drive etc. everything going well, then after some time had elapsed, dreaded DPF warning light came on. So as it was still under Guarantee, ( very much so) car was returned to the Dealership where it had been purchased. Usual diagnostics etc, and Service Manager informed the Lady that it would not be covered under guarantee, as the problem was caused by the driver. ( this was true, as the said Lady's job involved lots of short distance driving, loads of stopping and starting.) So Garage denied all responsibility, even when asked why this was not made clear when the Lady was negotiating to buy the car, as it was totally unsuitable for her needs. The Garage still refused to do anything, so the case ended up in court, and the Judge found in favour of the Lady, and the dealership had to take back the car, and refund the money. Needless to say, the Lady purchased a different car, and from a different dealership. This happened several years ago, but even today, the mention of DPF is enough to give anyone the shivers. However, having said that, It seems that now there are professional DPF cleaning company's around, and they can be cleaned to original specs....you will have to remove the DPF and deliver it to them, and re-install it when it has been cleaned. Apparently, as it is the original factory fitted DPF, the computer recognises it, and no programming is needed, Anyone have any experience of this? There are several video's on YouTube showing the procedure... May offer a ray of hope to some one !!!! 
You have my sympathy Leo46.......I'm new to Mercedes too, and reading you post has given me the willies....
I could not agree more Stu....New DPF every time. But necessity being the mother of invention ( or in this case profit... ) some enterprising people have developed cleaning programmes for clogged DPF's, and a local company are doing it here, you have to bring the clogged DPF to them, they will clean it. One of their selling points being that as its the original DPF, no reprogramming is needed when it's re-fitted. I really don't know a lot about this, but given the level of electronics now in cars, ( in some cases, even when changing a bulb ) and given the importance of the DPF, not too surprising that there would be a high level of interest in the computer on the DPF performance. As to what would stop a regen..I'm not an expert here either....but I imagine, short start / stop trips would not help...and what about interrupted regens ?? What else would you consider as an underlying cause?
I'll be knocking on his door next!And he may well refuse to accept it, if he is adept at such practices.
Interesting item,
http://ukprocessserver.blogspot.co.uk/2014/10/what-is-process-server-how-do-i.html
The next step could be a Process Server to ensure that your letter is 'delivered' to him. The 'easy' way to do it would be for someone to ask a Test Drive in one of the vehicles that he is offering for sale and then, part way through the drive, "By the way, I have this for you."
Agreed. Follow the due process of law. That keeps you on the right side of it for starters.
