Loco stalling on insulated track, why?

[cndctr111]

I have two sections of insulated track on my outer loop that when the train goes over it activates an accessory. For some reason I have 2-3 locomotives that whenever they get to the insulated track they stop dead, all of my other Marx locomotives run perfectly well over these sections. Does anyone have any clue why this is happening or if there is a fix for it? I'm befuddled.

Dino

[Terry]

Current will follow the path of least resistance. This means something on those 2 locos has higher resistance than the accessory.

Try cleaning the brushes and commutators on the two locos that stop.

If the locos run thru ok in the opposite direction the wheels are dirty.  Clean the wheels.

Also, wipe the track down with a dry Scotchbright pad.

[cndctr111]

Thank you much!

[starfire700]

Is it possible that the wheels on one side of these 2 locos have been insulated? I have run across a few that were converted or at least started to be converted to 2-rail, but the guy gave up of converted it back. You can check for continuity between the 2 wheels on an axle, or bench-test with leads to center and alternate wheels.