XPS 18 Tablet not charging while plugged in??

This is a very serious issue for many of us.  Where I work we have several Dell XPS 18 computers that failed with what I call the "charge port issue", some within days of the warranty expiring.  We have many in the field and the outlook is very grim.  There can be other charging issues like failed batteries (another big problem we are seeing), damaged pins on the base and such, but this post is specific to the failure of the normal charge port that you would plug the charger directly into.

The symptoms (independent of the OS installed to simplify discussion) are these:

Number one: The XPS will boot and operate, but will immediately shut off if the adapter is unplugged from the charge port. 

Number 2: If you enter the built-in diagnostics, you will see that the battery is not charging.  The adapter is supplying enough power to run the system, nothing more.  In most cases you will see no indication of the adapter type, it should show a 65 Watt adapter on the AC adapter row.  It will usually say "Unknown" for this failure.  It is not related to the adapter, if the adapter is not identified, the XPS will not charge from that adapter.

Number three:  The XPS will charge from the optional stand using the port on the long side, and the adapter is detected correctly.   Unfortunately we cannot access the stand port in our field applications.

There are probably variants to this where the charge port works but the stand port doesn't and such, but my interest at this time is limited to the syptoms described above.

It would seem there may be a problem reading the 3rd wire to the adapter that Dell uses to identify the adapter.  To the best of my knowledge Dell has repaired the XPS 18 for us under warranty by changing the motherboard after failing to fix it with the I/O board and bridge board.

Dell does not make parts available out of warranty in an easy or affordable manner.  They have told me to take it to a computer repair center.  I do most of the computer repairs for my employer so that was not very helpful.  When I did enlist the help of a local computer store they were told the mobo was $1094 new and a refurb was $749.99 but they had no refurbs in stock.  It took a couple of hours on the phone  to get the prices.  I would be very leery of a refurbished board unless it had this problem and the *DESIGN ISSUE* was solved and the repair included the solution.  The cost of a new board is well over half the cost of a new XPS.  They may include a new processor with the board which would add to appreciably to the cost, but it is not cost effective to repair them at a $1100 each with no warranty going forward.

If anyone knows of a company that can repair the motherboards with this problem I would be interested in discussing options with them.  I also would be interested in any schematic info or repair info for this problem that anyone knows about so I might diagnose or repair them in-house.   I suspect the fix might be rather simple if I could find what component is failing.    I have rework experience on SMT boards.  Somewhere there is a board test system that was/is used to test these boards for Dell, any ideas who that vendor is?  Dell is not being very helpful at this point.  I welcome them to step up and help.