I experienced a dearth of service info on this car many years ago. Since then I've had several from collections pass through my hands. Fortunately, most of their issues involved the truck shoes and old wiring, common issues for a variety of PW cars and easy to repair.
But it is rather curious that as early a PW release the Merchandise Car was, 'someone' didn't generate the common service documents/procedures/tips/hints as are typically found in the Greenberg et al, service manuals. It still seems like a witch-hunt to find published help. I have to wonder why this is? I would have at least expected some enterprising individual from the vast and past Lionel factory/authorized service stations to have replicated the documents in their classic format. After all, there have been multiple publications/magazines in which such work might have been published...and $rewarded$, even!
And here we are on the best forum in which to find the most obscure information...recorded in the
ELECTRICAL REFERENCE MATERIALS & MANUALS
section of the Electrical Forum...and, 
Further to this car's history, I also wonder why among the several modern era "celebration" remakes of the most reliable/notable PW operating cars, this one has never been re-issued?? It is, indeed, a close kin of the more ubiquitous Milk/Bosco/Hot Chocolate/et al, cars. Besides, what could be more 'realistic' than a UPS/USPS/Fedex/Amazon/et al version of a car that has someone throwing packages out of car halfway across the room??? (You know, that '18 volt experience'!)
And, hey, after the reindeer/sleigh/fat sack/chimney thing about Santa's delivery modus operandi wears off as we drink enough Anheuser-Busch 'Kool-Aid' truth serum in our later years, a Christmas version with the chubby red-dressed/capped, white-bearded Polar Elf himself heaving brightly colored (red & green) gift packages out the gaily decorated boxcar towards an equally gaily decorated house would be just the thing for a modern version of the tradition beneath the tree!
Or, if you're so deflated by inflation, a Grinch version for the UCS track at the edge of the table?
KD
