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Motor continuity/short problem

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Pilar Valley Railway:
I have searched on here for this topic with no luck.

I just ran into this problem after about a hundred RailPro installs in all different makes and models of engines.

I installed an LM3S in a Stewart AS-16. As soon as I put the engine on the test track to program it the warning ⚠️ came up for "motor over peak current". I couldn't even set the load.

I checked to make sure the frame and motor were isolated, made sure all wire connections were good. Everything was as it should be. Tried it again and the same problem.

So I unhooked the motor and removed it. Tried just the motor on DC and it worked great and before this install the engine ran on DC for a while.

So I took a multimeter and set it to continuity (the beep), and put a lead on each wire of the motor as it was sitting on my bench unhooked from everything. The motor leads had continuity between the positive and negative leads. If I'm thinking right that means the motor has a short.

So I had a brand new Atlas motor which has never been installed. I tested this motor in the same manner. It also had the same result. I then tested 2 different brand new Athearn motors and they DID NOT have electrical continuity. I then tested a couple more odd ball used motors I have lying around. Those also did not have continuity.

I ended up installing one of the new Athearn motors in the engine and everything is working fine.


So my question is.... Has anyone else experienced this problem??

gregeusa:
Testing for continuity might work (probably should), but it's much better to test under running conditions.

Set up to measure amps and volts at same time (2 cheap meters like Harbor Freight for $5 each is enough)

Check the no load amps at several voltages, and then load the motor down (grab with a glove, etc) and look at current under heavy load.

Finally stall the motor completely and measure the current. That is TRUE stall current.

Greg

Pilar Valley Railway:
Thanks Greg, but either you didn't understand what I was saying or I didn't say it right.

The LM3S thinks there is a short with the motor because there is continuity between the 2 motor leads on a couple of the motors I have. But the motors work fine just testing them on DC.

KB02:
Are there any resistors connected to the motor? Some DC motors will have resistors (at least I think they're resistors) connected to them to help aid in smoother running on DC power. Most DCC conversions require the removal of these resistors. Bachmann locos are like this. Not so sure about Stewart.

Pilar Valley Railway:
There are no resistors. It's just the motor sitting on my bench not installed in anything.

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