AF Alco dummy headlight - can't figure out "wiring"

The chassis is the common or return via one truck. The other truck  is the hot lead.
The trucks wheels are insulated on one side and not on the other so one truck frame becomes the hot voltage and the other the common voltage.  The one truck should have the wheel insulators on the opposite side of the other truck. The hot truck should be insulated from the chassis by fiber washers at the top of the yoke.

One lead of the replacement socket should be connected to the chassis the other to the hot lead from the truck with the power lead.

If this is not working then the wheels may be dirty on the trucks?

 

This is so frustrating.  I realized I have a second dummy Alco A that I'm using the shell to put on a Rocket.  Look at picture (way above) Here's what I've tried -

1) first dummy, both trucks insulated from frame, wire take-offs on truck posts thru frame, using second dummy trucks w/o shoes                                                                = no light unless touch any of 4 wheels on near side of loco (use pic above)  

2) first dummy, both trucks insulated from frame, wire take-offs on truck posts thru frame, using first dummy trucks with shoes     SHORT CIRCUIT

I can light a bulb by touching any pair of opposite wheels (say wheel one on one side to any wheel on opposite side)

I can put on the rear truck is fine (no light), when I put on the front truck with shoe it shorts out. 

It would seem there's no dead short anywhere because of #1

Thanks for any suggestions -

Tom

AHHHHH!!!!!    Turn the rear truck 180 !     LOL

REAL WORLD INTRUDES                    So I was right in the beginning about how the rear truck was facing was an issue, not sure what the heck is going on, but by turning the truck around I've been able to get the headlight to work - I used the truck frames without the shoes, the ones with the shoes still shorted out the dummy. BUT now the rear truck doesn't clear the rear the single plastic step on the rear of the 21922-1.  This dummy engine has a factory defect on the paint on one side anyway - the long MISSOURI PACIFIC  and engine # have "bad spray" and you see small dots of missing paint - so I'm considering just cutting off one side of the steps .  Oh, of course, stripped screws, I think I got 4 to work.   So, I don't know why this works this way electrically, but I got it to work.  Thanks for the suggestions -

Tom

I don't have any Alco parts handy to look at, but the sliding shoe on the truck sideframe determines which side the uninsulated wheels are on; they should be on the same rail! It's easy for someone to put new wheels & axles on backwards when servicing the engine. The sideframes should clear that step, and cutting it off is NOT a good idea! Typically, the front, or nose truck would be the insulated one, and the rear end truck would be the uninsulated truck--this only true on late production units, prior to that, most chassis were neutral.

Hi - yah, I can't see the electrical rhyme nor reason for this particular engine - funny, I also thought to take off the trucks and reverse first the rear and then the front 4-wheel assembly, in every combo of assemblies the trucks with shoes are a dead short, but by using the shoeless trucks off an old Sante Fe dummy and reversing both 4-wheel assemblies at least I don't have to cut the truck off - thanks for the help. So are all wheels conductive but the axles are not?  All my wheels seem to be conductive - they are all brass I thought, I'll have to look again -

Tom

Now the issue is the rear coupler hangs down too low and hits the tops of my re-railers and disconnects this engine ... I have this issue with several cars, too, I'm going to have to look into "fixing" couplers   

  All my wheels seem to be conductive - they are all brass I thought, I'll have to look again -

There has to be insulation somewhere. Perhaps a plastic bushing between the axle and the wheel.

Perhaps you can use a continuity tester (or meter) to check each wheel to the axle. For each wheel set, one wheel should be insulated from the axle, and the other should have continuity.

Maybe one or more wheel sets is installed backwards, or maybe you have a bad wheel set.
These things happen.

  From reading, Id have to guess the wheel sets are in reversed or you are missing isolation on something somewhere.

Yes, the wheels are bronze or a slintered metal, however the insulated ones have a white plastic center that presses on the axle, and keeps the back side of the wheel way from the truck frame, so it can't short against it. It's pretty easy to see if you look down the backside of the wheel. In fact, you can see them on the wheels in your first posting's picture. OK, I looked at my locomotives, If you hold the locomotive upside down, the nose truck will have the sliding shoe on the left side, that is also the side that should have the power pickup wheel--on a pullmore engine, the rear wheel (farthest from the coupler) will be a pull-more wheel, and doesn't really pick up power because of the pull-more rubber surface. Looking at your picture in the first posting shows the wheels ARE on backwards!! I think we found the problem.

PS it could even be a factory error! I've seen such things before on other ACG locos. I don't know how they got passed testing, but since there's no motor in it, maybe it wasn't run on the testing/packaging tracks.