Trouble with Williams 72' streamlined passenger trucks

I am currently converting my Williams 72' passenger cars to use LED lighting strips.  I have experienced some of the same problems with wiring to the pickup rollers.  The first thing you need to do is to stop the wire from moving around in the gap in the frame.  Wrap a small piece of electrical tape around the wire where it passes the frame and jam it into the gap between the frame and the light fixture.  Leave enough slack wire to the pickup roller so that the trucks can turn both ways, but not so much that it touches the wheel.

Also, tug on the connection to the pickup roller (where the small piece of heat shrink tubing is) because I have found some of those connections either loose or broken.  If it is you have to re-solder the wire to pickup roller.  Sorry, but that's the way it is with these cars.  Otherwise, they are great looking cars and I have several sets.

To clean the pickup rollers I use electrical Contact Cleaner in a spray can.  I lay the car on its side and put a paper towel behind and below the pickup roller.  I spray the contact cleaner between the pin and the roller, letting it flow through the inside of the roller.   Then I spin the roller a few times and spray it again.  Almost always, a black spot will appear on the towel below the roller from all the gunk inside the roller, even on rollers that appear to be clean on the outside. 

I have several of them and I haven't had the wire issue. I would suggest trying to reposition the wires to prevent the chafing issue.

I use the Bachmann conductive lube on my rollers and it works great.  I think you should try to clean the rollers as Roger suggested and relubricate. Make sure you don't get contact cleaner on the painted parts of the car. I use it at work and it will damage some paints. The paper towel Roger suggested, I would guess, is to catch the contact cleaner and minimize the chance it will get on the paint. You could try rubbing alcohol, 91% (that is available most anywhere for a lot cheaper and easier to find than contact cleaner) and use a pipette to flush the rollers with. That is the way I clean my rollers.