Sparking/shorting old Craftsman 3/4 HP motor

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Forum topic by ppg677 posted 03-24-2017 03:18 PM 1005 views 0 times favorited 3 replies Add to Favorites Watch
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202 posts in 1032 days

03-24-2017 03:18 PM

I’ve been running a 60-year old Craftsman 3/4 HP motor. I replaced capacitor a few months ago and motor had been working great.

Tonight it wouldn’t turn on and just buzzed. I opened it up slightly (not all the way because I didn’t feel like disconnecting wires). It was filled with wood chips and dust. I vacuumed some of that out. Squirted some 3-IN-ONE electric motor oil on the centrifugal switch, and bolted her back together.

Motor fires up again just fine but I’m noticed a brief spark inside when it spins up every time I turn it on. I also detect a smell. The spark is not in the same spot every time which is odd.

My careless squirting of 3-in-one oil? Or something worse going on?

Any tips for fixing this? I’ve had this motor completely apart before. Not looking forward to taking it apart again, but sure has been a nice/powerful motor.

3 replies so far

View Rrrandy's profile


212 posts in 655 days

#1 posted 03-27-2017 02:08 AM

ppg667, the motor is 60 years old…don’t be cruel, lay it to rest.

-- Y'all need to locate a sense of humor. Borrow one if you can't find yours...

View MrUnix's profile


7005 posts in 2375 days

#2 posted 03-27-2017 02:21 AM

ppg667, the motor is 60 years old…don t be cruel, lay it to rest.
- Rrrandy

Nonsense… I have motors at least that old or older that still run as good as new!

Oil in an electric motor is never a good idea, unless it’s applied very sparingly to specific parts, such as the moving bits on a centrifugal switch. I would open up the motor and clean it out good with a rag and compressed air (not a vacuum). Doing so will also give you a chance to check the wiring and other components, and maybe even see where (or why) there was some sparking. While you have it open, if it has sealed bearings, replace them (unless you have already within the last few decades or so). Worn bearings can also give enough wiggle room to let things touch that shouldn’t be – which would cause sparking as well. There is not a lot that can go bad on an induction motor other than normal maintenance items – bearings, the capacitor and the start circuit (centrifugal switch). Properly maintained, they will last virtually forever.


-- Brad in FL - In Dog I trust... everything else is questionable

View ppg677's profile


202 posts in 1032 days

#3 posted 03-27-2017 04:50 PM

I think I killed the motor :-/. Put her back together after taking it apart. Applying power led to smoke/sparks. Not from inside the motor but from the lead wires.

I ended up going to Harbor Freight and spending $110 on a 1.5hp motor. Way overkill for this 6” jointer but it is the only thing they had in the ~3450 RPM range.

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