Model Power Pacific DCC short

[peteski]

Peteski's idea of the crank pin hitting the wipers was right on. I pulled it out a bit and the short went away.
I removed it and shortened it a bit and re installed- no more short.
Thanks- don't know how I would have ever found that one.

You're welcome! 
Seriously though, while I was looking for a possible source of a short, and looking at the wheel wipers under very strong light,  I just happened to notice that the main crank pin was sticking way past the wheel back!  I had the loco running slowly upside down in a cradle and the light made the metal crank pin flash in that deep dark area between the loco's frame and the back of the wheel.  That got me thinking that the crank pin was getting dangerously close to the wheel wiper. Mine was not shorting, but I figured that it was worth mentioning.  I got lucky. I'm glad that it resolved your problem.

[woodone]

Peteski, even with your point about the pin sticking through the driver I was unable to see the contact with the wiper strip.
One of my biggest problems is with most small screws and small parts is they are black. Black on black is very hard for me to see.
Any way one thing I noticed on this crank pin was that it had a very small sharp point on the tip. Looked like it should of been removed in the manufacturing process. It stuck out quite a bit.   

[mmagliaro]

Peteski, even with your point about the pin sticking through the driver I was unable to see the contact with the wiper strip.
One of my biggest problems is with most small screws and small parts is they are black. Black on black is very hard for me to see.
Any way one thing I noticed on this crank pin was that it had a very small sharp point on the tip. Looked like it should of been removed in the manufacturing process. It stuck out quite a bit.

Oh... now that part I know about.  Most of the crankpins (maybe all) on the MP steam have a pointy tip.   Honestly, they look like a cheap wire nail when you pull them out of the wheel.

[peteski]

I didn't say that I saw the back of the crank pin contacting the pickup strip (mine wasn't shorting). But it looked like a likely culprit (if the pin  was just a scoobitch longer).  I also did not disassemble anything - just observed the loco running slowly upside down nested in a cradle.

Since dismantling N scale locos (and lots of other subminiature work) is a big part of my hobby, I have *LOTS* of light over my workbench and all sorts of magnifying implements. I have no problems seeing anything (even black on black items).  I have more problem threading the screws back in the holes. I can see them jost fine, but my hands are no longer rock steady like they were when I was in my 30s.

The main crankpin looks like a metal lost-wax casting to me. It is actually well made (similar to what is used in brass locos). Like Max said - it probably was not snipped off the sprue correctly, making it extra long. There are several other nice metal castings in this model (including the smokebox front).