Lionel 623 Switcher Problem

You have at least one worn bearing.  That motor should run smoothly and a lot more quiet than that.

Agree with Dan. Also check the commutator for a unsoldered wire. You might have a open comm. section.

Check the commutator segments for continuity among them, and shorts to the shaft.

Dan/Ed: I didn't see any unsoldered wire on the commutator. Before re-assembly, should the thrust bearings (2) be packed with grease for smoother/quieter running?

ADCX Rob: Using an Ohm Meter, the 3 commutator segments have continuity among them. Concerning shorts to the shaft, there is no continuity between the commutator segments and the shaft. Is this the way it should be?

@Anich posted:

Using an Ohm Meter, the 3 commutator segments have continuity among them. Concerning shorts to the shaft, there is no continuity between the commutator segments and the shaft. Is this the way it should be?

Yes, with equal resistance among the segments(A-B, A-C, B-C).

Just use oil on the trust washers.  Before you oil, examine the bearings for wear, after all they have been in there for 70 years.  If there are ridges or rough spots, replace them.

Here's a video showing the resistance between segments A-B, A-C and B-C. In your opinion, are the resistances close enough? Also, there is no continuity between the shaft and the segments. If the resistances are close enough, what's the next step in our diagnosis?

It looks okay to me.  I don’t think all the noise is electrical.  Examine the shaft, bearings and thrust washer for damage and wear.  Also check axial and radial movement of the armature shaft.  There should be no perceptible radial movement (side to side).  There should be a few thousands of axial play.  Radial play indicates a bad bushing.  Excessive axial play indicates bad or missing thrust washer(s).

Your first resistance check, A to B, shows zero resistance. The resistance should be about 1.7 ohms. Is the A to B slot shorted?  Might be time to start looking for a replacement armature.

@Anich posted:

Here's a video showing the resistance between segments A-B, A-C and B-C.

A is shorted to B. You need to figure out why.

So based on your comments, I started to think about what could be causing the short between segments A-B. The first thing I thought about was the slot between A-B. I always clean the slots between the segments whenever I service any of my engines, but this time I really cleaned out the slot between A-B. Then checked the resistance between the segments again and found that the resistance between segments A-B now shows a reading of ~1 ohm, similar to segments A-C and B-C (refer to attached video). I placed the locomotive on my test track and it ran.  I oiled the thrust bearings on the armature shaft and placed the locomotive on my platform. Now it runs great (refer to attached video). I never realized how important it was to keep the slots between the segments clean in order to maintain a smooth running locomotive. Thanks to Dan, Ed Horan, Rob and David Johnston for your extremely helpful comments.