I recently acquired an old monorail set, and I'm having problems getting it to work properly. It works fine on normal track, and it is able to continue on or stop at a monoswitch when the switch is set accordingly.

However, it isn't always able to reverse directions (it often just stops) at a monoswitch, and once stopped, the switch usually isn't able to get it started again. It seems like the switch on the side of the motor isn't quite getting pushed all the way in. It runs fine again once I push the switch all the way in.

The behavior is somewhat dependent on direction. Although it isn't able to start from a stop at a monoswitch in either direction, it is more often able to reverse direction going one way than the other.

I'm wondering if anyone has experienced this behavior, and if there is a way to fix it.

If it makes any difference, the motor is from 6990 from 1987.

  • Are you using a fresh, non-rechargeable battery? It could be that the monorail doesn't have enough forward momentum to push the button all the way.
    – Joubarc
    Commented Nov 29, 2012 at 8:15
  • 1
    I am using a fresh battery. I've also tried powering the motor with a 9v train controller, and the behavior is the same.
    – jncraton
    Commented Nov 29, 2012 at 11:32
  • Using a 9V train controller is a better idea than a fresh battery, so we can probably rule out the motor not getting enough power. However, it could still be weak on its own, but it's also true these monorails never went really fast to start with. A mechanical issue maybe? Is it hard too push the motor switch manually? If it hasn't been used much, maybe it needs some wear & tear.
    – Joubarc
    Commented Nov 29, 2012 at 15:24
  • Also, does the problem happen on both sides? If you turn the motor around, I mean? I know these are fairly straightforward questions, but I can't think of anything else at the moment (hey, at least I'm not asking if you turned the switch correctly)
    – Joubarc
    Commented Nov 29, 2012 at 15:31
  • That's a good point. I updated my question to include this information.
    – jncraton
    Commented Nov 29, 2012 at 15:47

1 Answer 1


Maybe the plastic is worn off just enough that the switch is not pushing the pins completely anymore.

Debug step 1: When the train pins are in the switch zone there shouldn't be a lot of space between the point of the pins and the face of the switch. If it looks too loose that could be the problem. A way to test this would be to put some clear scotch tape on the faces of the switch. The faces are highlighted in red in this picture:

enter image description here

If the problem persist you could add more layer(s) and test again. After four layers if this doesn't fix the problem I would try something else.

Results: The switch works with four layers of tape. The new question is "Between the motor pins and the switch, which one is worn out? One or both?"

Debug step 2: Testing the switch with a second motor would be helpful. Do you have a second motor? In any case let's inspect the motor pins and the switch faces.

The two motor pins are (I assume) made of plastic. The end point of each pin should not not be worn down. One way to check that is to compare the two. If one is rounder then the other that gives us important information.

The switch faces (highlighted in red in the previous picture) should be a perfectly flat surface. Is there a slight groove at the height where the motor pins hit the switch? Again. this would be important information.

Results: The switch faces are not worn but it looks like the motor pins are rounded off.

Debug step 3: Testing & fixing the motor pins.

Before trying to fix the motor pins I would suggest one last test. With no tape on the switch, you could add tape layers to the motor pins and try to reproduce the successful test of step 1. This should work without problems.

As for fixing the motor pins. I would suggest to use one epoxy glue drop at the tip of each pin. After the epoxy is cured you could test and if necessary sand off any excess thickness.

Results: Epoxy on the motor pins fixed the problem.

  • 2
    Thanks for answer. Four pieces of tape does narrow the gap about the right amount to make the monoswitch function properly. I had actually considered something like this as a solution, but I wanted to make sure that I didn't fix the wrong part. If it's really the switch on the motor that is the problem, I'd hate to narrow the gap on the monoswitch so that a good motor won't even fit through it. I'd love to hear what you would recommend as a permanent fix.
    – jncraton
    Commented Dec 8, 2012 at 13:58
  • I unfortunately don't have another motor to compare with. The monoswitches don't look visually worn down. I have compared the pins on my motor to pictures of others around the net, and I think they may be somewhat rounded off.
    – jncraton
    Commented Dec 8, 2012 at 14:56
  • Good. How about the switch faces? Are they worn? Is there a groove?
    – pcantin
    Commented Dec 8, 2012 at 15:37
  • They don't look worn down.
    – jncraton
    Commented Dec 8, 2012 at 15:45
  • 2
    I put a bit of epoxy on each end of the motor switch and filed it back down to a point. This seems to have resolved the problem. Thanks!
    – jncraton
    Commented Dec 9, 2012 at 21:23

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