oh no!!Truck Sparking

You have to pin down where on the trucks the sparking is occurring:  wheels, pickup rollers, elsewhere, etc. 

I sparks anywhere it touches the chassis.

Check the wires from the pickup rollers, where they go through the frame and alongside the motor.

Is this a short circuit spark or the making and breaking produced by a bad contact? 

When you say "where it touches the chassis," I'm not clear, because the truck always touches the frame where it comes through it.

I can unscrew the red wires from the trucks and just hook them up via alligator clips and take another jumper from the frame to the truck and it sparks.

When it is altogether you can put it on the track and as the truck moves you can see sparks from around where the motor is touching the frame.

I have checked all the wires and see no bare places anywhere.

 I just found one of my 2 rail conversions is sparking at the truck. It appears just the one and only on one side. I believe it's a brake shoe that is too close to the wheel and sparking more on corners when there's no gap.

 I don't think that would help here as you're probably three rail?

I did have an engine that the red wire rubbed or bent just right would spark. I had to clean up the loose, poor connection, and I added heat shrink to insulate. It looked OK but there were eventually marks from arcing.

"you can see sparks from around where the motor is touching the frame."

I had one that the motor wire was touching the casing when the wire got tight on corners.

 This is interesting to me. Will watch for the results.

Chuck, Ear Joe raises a good point.  This is 3-rail, isn't it?

I would take an ohmmeter and go over the truck and wiring, removing the truck from the loco.  I recommend against trying to run it under power, for the sparking might injure the electronics.

My recollection is that the motor shell is insulated from the frame, but admittedly I've never had a need to examine it closely.

Check to make sure that where the wires are soldered to the motor brushes, that neither tab is bent and touching the motor shell.

Also check that one of the pick up rollers is not contacting the frame of the truck when stressed

OK, here is the solution.

The black wire that attaches to the truck uses a black screw. it does not conduct.

So the solution is either replace it with a nickel screw or grind under the head so that it makes good contact.

This was per MTH technicians.

It worked!!!

Now I have a Blue Comet PS3 that is sparking at the trailing truck.

Took out the engine board and tach reader

Any ideas????

Chuck, when the sparks appear, are the trucks on anything other than plain track, like switches, uncouplers, etc."

Are the trucks picking something up from the layout?

I have it on the bench on it's side hooked up with alligator clips, I can start it up and move the truck around and it sparks.

Sounds like the power wire to the truck may be pinched or have some missing insulation and is shorting.

Can't you see exactly where the sparks occur?  Sometime roller brackets fail to keep the roller or the bracket from touching the frame.  Or the screw holding the bracket can be loose.  Or the insulating block may have cracked.

I've seen a couple where the wire to the pickups where chaffed and sparked on the frame when the truck moved or turned.

Keep in mind that this is a steam engine and it is the 2 wheel trailing wheels that are sparking. Not a powered truck with rollers.

Does the truck have a finger that contacts the axle?  Shouldnthere be one and it's missing?  IS it light sparking, like Lionel Pulmors do at the roller, or a heavy spark like a short?

If there isn't sufficient contact through other wheels, maybe those trailing truck wheels are carrying much of the current.  If so, the sparking might just be for that reason.

I have an MTH BiPolar, we call it "Ole Sparky".  It sparks down low on the truck when wheeling around the layout, off and on.  Spent hours literally trying to figure it out.  Never did find the problem and it runs fine without tripping any breakers or burning up, so we just live with Ole Sparky.  Smoke unit doesn't work very well and never did, sputters and spits.  Nice discoloration now around the smoke stack.  Not too much or two little fluid, just the way it is. 

Where are your clips hooked up to? Does the trailing wheel have wires for pickup?

I assume your talking three rail? is this 3/2 model?

You really need to post more facts if you want help with this. Guessing what's arcing and why is impossible to get right.

 How about a picture of the area?

Chuck, you have to state exactly where you see the sparks at the trucks.

I will let you know when I get it back on the bench. I am waiting on a tach sensor for it.

Jumping the gun a bit, but going with Gun Runner Johns point. Could the tender be pulling current trough the drawbar. I've also seen a few "Sparkys" over the years, mostly pulmor switchers, or plastic motor Scouts though. Clean the wheels & track lately?   

Adriatic, yes it is possible.  If loco is not getting good ground feed from outside rails, such as might be caused by traction tires and poorly connected trucks, feed could come through drawbar.

Could the tender be pulling current trough the drawbar

This is a PS3 engine so the answer is no, not through the drawbar per se. The drawbar is not made of metal or any other electrically conductive material.

Rather, the drawbar is a ruggedized circuit board that connects Common from the tender to the engine by intention, through one of its internal circuits.

Good point,  Barry.  I had forgotten this is PS3.  I haven't looked at the drawbar connections.  Could there be a loose wire or a dangling strand?

Robert,

Could there be a loose wire or a dangling strand?

That would be very unlikely.