Intermittent Drum Switch Operation

[Rick Kruger]

Reversing a DC motor while it's running, by changing the polarity of either the armature or field, is called "plug reversing". If you do it at full speed it can damage the motor. The AP (Anti-Plugging) relay prevents you from plug reversing the motor.

You can bypass the AP relay by connecting between these two terminals:

Do not use either of the coil terminals on the side! It would be cleaner to connect to the terminals on the back of the panel.

I now see why your AP relay isn't working. The braided copper wire is not original. The original wire was tinned copper and connected to the moving contact arm via a small hole at the top of the arm:
View attachment 394236
The original wire appears to be soldered to the arm. Without the wire, the AP relay won't operate reliably.

Not entirely clear on what you are seeing. Here are better photos of my wiring and contacts. The unraveled bare copper wire appears firmly connect to the arm.

If I can get the rely working reliably by rewiring, I sure rather do that than bypass it.

Rick

 

[Rick Kruger]

...snip...
You can bypass the AP relay by connecting between these two terminals:

Like this. I can put the contactor arm back in place, for "safe keeping". But, if there is a fix that gets the relay working properly, I'd rather do that.

Rick

 

[Cal Haines]

Like this. I can put the contactor arm back in place, for "safe keeping". But, if there is a fix that gets the relay working properly, I'd rather do that.

Rick

View attachment 394247

I would set the contact arm aside for now. See if that solves your startup problem and report back.

 

[Rick Kruger]

I would set the contact arm aside for now. See if that solves your startup problem and report back.

Jumper seems to have worked. No failures to start during a short work session. Will know better after a few days use.

Thanks,

Rick