Mk5 motor is dead

[ChrisNeilan]

crud in the contacts = no current through the contacts = no current in the "start" winding = no start.

I don't expect the problem to return. No hum + no motion was the first clue for me.

The RUN windings are directly connected across the power input wires. When those wires are energized, the motor hums quite loudly.

Only the start circuit is affected by the start switch.

Do recall the admonition to NOT leave the motor energized when the start switch is open since the run windings will 'fry'.

No hum means the run windings are NOT being energized. Only the power cord, plug, power switch and splices will cause that(as well as a dead outlet).

It may not return, but we know not why 'no hum'.

We know why- Gremlins!

[trainguytom]

Well, after 2 days of running just fine, the same thing happened. One thing I failed to mention in my initial post that happened when the fail occurred. when I flipped the on switch, there was an ever so brief "bump"...don't know exactly how to describe it. It was as if the start impulse was going to happen, then it instantly disconnected. Flip switch...shaft (with sanding disc on it) did a quick little jerk as if it was going to rotate...then nothing. No hum, just nothing as if there was no power to the motor. Subsequent on switch flips got nothing.

Very frustrating.

So, to move on, I switched in my backup motor, but It is making me kind of nuts, not knowing what's going on. I did blow out the motor again, since that seemed to do the trick the first time, but to no avail.
I've restored probably 20 mk5's, many that were very sad to begin with, put bearings in most of the various motors, and never had any motor issues. As a result, I've come to think of all of them as infallible.
I guess that's why this bugs me. Also, I'm no an electrical engineer, so I'm not wanting to get too deeply into the hard core electrical stuff, meters, resistance, etc.

I was hoping for a more basic mechanical solution. (dirt, bad connection, etc.)

I know there are guys here that go way beyond basics on this forum, and I appreciate their input, but I don't have the time or energy to follow up on that. (hence, the backup motor replacement)
What frustrates me is having to junk this motor when it may not need it, just because it's beyond me to fix it.

Wow...this has gotten to be a really long post. Guess I needed to vent.

[beeg]

Are you sure it's not a bad switch?

[trainguytom]

Are you sure it's not a bad switch?

Been through all this before. NOT a bad switch, cord, outlet, etc. I'm using the same switch on the changed in motor, same outlet, etc. All works fine. In fact, the failure occurred using a new switch (verified to work) that I had on hand. So definitely not a switch.
Oh well, the other motor works fine. Not sure whether I should toss the non-runner or keep it to agonize about getting it to run later.

[JPG]

Are you sure it's not a bad switch?

Been through all this before. NOT a bad switch, cord, outlet, etc. I'm using the same switch on the changed in motor, same outlet, etc. All works fine. In fact, the failure occurred using a new switch (verified to work) that I had on hand. So definitely not a switch.
Oh well, the other motor works fine. Not sure whether I should toss the non-runner or keep it to agonize about getting it to run later.

I think we are down to an open internal splice or an intermittent power lead.

[everettdavis]

Is this a GE motor? Notorious for cracked decayed wiring on motor leads.

Does it have centrifugal motor start switch or external motor start relay?

Could you have a broken wire that makes contact intermittently in the power cord? Depends on how you coil it whether conductor is pulled apart or connects.

Everett

[trainguytom]

Here's a pic of the motor. Not sure if I should save to screw with later or just junk it. Not sure if the pic shows up. I tried to upload it, but I can't see it.

[trainguytom]

the motor is an Emerson model # C55DDR-2015C

[JPG]

Here's a pic of the motor. Not sure if I should save to screw with later or just junk it. Not sure if the pic shows up. I tried to upload it, but I can't see it.

Since the problem cause has yet to be identified, junking it is premature.