Engines don't move.....

[LIRR]

I have two Bachmann locos that work very well.....however, sometime they stall. Light is still on, bell & whistle works, sound revs up as I open the throttle, but it doesn't move. Happens to both locos I own. It also happens in the same area, maybe 2 loco lengths. Track has power, otherwise no sound, right?

I'm stumped.....

[Mark W]

First thought is to check for voltage drop.  They may be getting enough to enable sound, but not enough to feed the motor.

[peteski]

How do you get them to move again?
Maybe there is a fractured wire (or intermittent connection at the connector) in the wire harness supplying power to the motor?

[LIRR]

To get them moving I give them a push....I thought about intermittent contact internally, but it's only in one area, both work perfectly everywhere else. I just spent 15 minutes shuttling a loco back and forth thru this area and it didn't happen. It only happpens (sometimes) when the loco comes to a stop to uncouple or changed direction. It never stops moving on its own....

[John]

clean the wheels?

[peteski]

Cleaning the wheels (and track) is highly recommended 1st step of troubleshooting.
What is puzzling is that when the loco stalls the functions (headlights) and sounds still work. That would seem to indicate that the electrical contact is good.  It seems to me that the problem is in the motor circuit or possibly mechanical binding.

When the loco is stalled, do you crank the throttle slightly to try to get it to move, or have you cranked the throttle all the way up to maximum speed?  If you haven't cranked up pall the ways, try that. Also try do do the same in reverse direction of when the loco stalled (all without touching the model).

[LIRR]

Wheels and track are as clean, i can give it full throttle and it gets louder but won't move. The odd thing is that it's only in this one vicinity.....

[thomasjmdavis]

Wheels and track are as clean, i can give it full throttle and it gets louder but won't move. The odd thing is that it's only in this one vicinity.....

Questions that occur to me-
First, Bachmann makes a lot of locos- what specifically are these? I had an issue with my last layout where a bit of track kinked (humidity, I am guessing) on a curve, and a long wheelbase loco wedged itself at that location when moving slowly.
Is the affected area at the top or bottom of a steep grade?
Do any of your other locos experience any kind of power fluctuation in the same location? 
Do you have another loco with the same decoder that has no problems? 
Is there a turnout anywhere in the vicinity? 
Does a meter show the same power at the rails at that location as at other locations? 
Do the locos behave the same way whether running individually or together? 
If they hit the area at high speed, do they breeze right through or hit the brakes?
Do you have one big power block or several separate power blocks?  If the latter, is the affected area over insulators between two power blocks?  If the former, is the area at the far point from the power block?

This is the sort of thing I used to encounter all the time on various DC layouts.  But the lights/sound staying on makes this a mystery. Still, the info that it stops at a particular place and then moves when you push it makes it sound like a track/contact/power issue at that particular location.

[LIRR]

locos are RS3s, problem area is near a switch, straight track on both sides, no grade here. every piece of rail has its own feeder, frog is wired. loco is never stopped on the switch when this happens.
both of my (only 2) locos experience the same issue in the same location, but nowhere else... 
the locos behave the same way running individually, I do not run them together 
they breeze right through the area, it occurs after I stop the loco to change direction or uncouple....
right now, I have one power block (not very big really), the area is within 10 linear feet of the main connection from the powercab to power panel

[nickelplate759]

Some thoughts to help troubleshoot.

Hypothesis 1 : something about the specific track area is the problem, not the locomotives.  Can you test this with a borrowed locomotive that isn't similar to yours?

Assume it's the track area - it's either electrical or mechanical (assume it's not haunted).
If it's mechanical, you should be able to detect it with an NMRA gauge.
If it's not mechanical, it's likely to be electrical.

Assume it's electrical:

Hypothesis 2 : The problem is actually that the DCC signal is marginal in this area.
What gauge and length are your feeder wires to the problem track?   
Have you checked the electrical  resistance through  each feeder to it's corresponding piece of rail?  If there's a poor connection somewhere I think that it could mess up the DCC signal under load.

That's how I'd start to chase this problem.

[davefoxx]

^ This.  I agree with George: it's something in the track that the Bachmann locomotives are just more sensitive to than other brands of locomotives.  Double-check that the track is clean, check that the rails are in gauge, and check that there's not some sort of voltage drop or poor connection affecting the DCC signal.

DFF

P.S.  Oh, and while you have the NMRA gauge out, check the gauge of the wheelsets on your Bachmann locomotives.

[CNR5529]

I have a Bachmann spectrum 2-8-0 (n scale) that displays the same symptoms, however I have determined it is not the track. At first, it would not move until I gave it a nudge, even though the lights were on. This would happen on any track/layout I tried the loco on. The problem has since deteriorated to the point where now I can hear the motor whine/buzz (and the lighting still works) as I throttle up to full throttle, but it does not turn over at all. The wheels and gear train were checked and no binding was found. Next will be testing the motor on its own with straight DC to see if it is burned out.

In my case the 2-8-0 has a DZ125 installed, and it worked well for years without issues. I have tried reprogramming the decoder and playing with the stability control with no luck. It appears to be a problem with either the motor control output on the decoder, or the motor itself.

I'll let you know what I find.

[peteski]

While the track seems to be the problem here, how do we explain the fact that everything except for the motor works ok?  The sound of the engine speeding up as the speed step is increased on the throttle seems to indicate that the loco is receiving and understanding the DCC speed step packets. The decoder should also be powering up the motor along with ramping up the engine sound.  The sound uses quite a bit of power so the voltage drop problem seems unlikely.  I would think that if there was enough of a voltage drop not to power the motor, the sound would also cut out.

Is there a function key which can mute the sound (like F8?). Maybe you should try to crank the speed to the max while confirming that the motor sound corresponds to the max throttle setting, then mute the sound and listen if the motor itself is making any noise (as if it is trying to run).

[LIRR]

Good idea Pete, turning the sound off, it just happened again (although about 1 -foot away from the usual spot), I turned off the sound and the motor was absolutely silent. An poor connection within the loco makes sense - other than why only in this area.....Why both locos I the same area.....

I shall open one up and see if there's anything amiss

[LIRR]

Good news I suppose, it happened in 2 other locations. I guess that rules out track and/or power problems. Every piece of rail either has its own feeder, or is soldered to the adjacent piece with a feeder. All of the locations so far have been within 10 linear feet along the 12 ga bus of the power panel. I only have the 2 locos, 1 idles as I run the other. The NCE Powercab is good for 2 amps (i will eventually upgrade to an SB5 booster more track goes down around the room), so i think power isn't the problem.....but of course i could be wrong.

Time to open up the locomotives