# electric motor sparking **URL:** \ **Category:** Factual Questions\ **Created:** [September 26, 2008, 4:46pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355 "2008-09-26T16:46:52Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\ **Post date:** [September 26, 2008, 4:46pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/1 "2008-09-26T16:46:52Z")
My Might Mite vacuum cleaner was grinding and starting to smell. I took it apart and ran the motor and saw tons of sparks streaming out of the area where the brushes make contact. I removed the brushes and found that there was tons of graphite left. Is my Mighty Mite junk? ---
**Author:** ![Carson\_O\_Genic](https://avatars.discourse-cdn.com/v4/letter/c/cdc98d/32.png) [@Carson\_O\_Genic](https://boards.straightdope.com/u/Carson_O_Genic)\ **Post date:** [September 26, 2008, 5:17pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/2 "2008-09-26T17:17:07Z")
Does the contact face of the brush(es) have one continuous arc from contact with the armature? ---
**Author:** ![HongKongFooey](https://avatars.discourse-cdn.com/v4/letter/h/c4cdca/32.png) [@HongKongFooey](https://boards.straightdope.com/u/HongKongFooey)\ **Post date:** [September 26, 2008, 5:17pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/3 "2008-09-26T17:17:18Z")
Are the ends of the brushes pitted? Are the springs or brush holders keeping them seated properly? How does the commutator surface look? There are a lot of reasons for a motor to spark. Can you see the electrodes when you look at the end of the brushes, sometimes even when they look like there is a lot left, they’ve worn down enough to expose the lead inside the brush (at least with larger motors I’ve seen that). ---
**Author:** ![Interconnected\_Series\_of\_Tubes](https://avatars.discourse-cdn.com/v4/letter/i/13edae/32.png) [@Interconnected\_Series\_of\_Tubes](https://boards.straightdope.com/u/Interconnected_Series_of_Tubes)\ **Post date:** [September 26, 2008, 5:21pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/4 "2008-09-26T17:21:11Z")
> [@solkoe](#): > > My Might Mite vacuum cleaner was grinding and starting to smell. I took it apart and ran the motor and saw tons of sparks streaming out of the area where the brushes make contact. I removed the brushes and found that there was tons of graphite left. Is my Mighty Mite junk? Having purchased three inflatable beds in the last year and having noticed that _all three_ of the included electric pumps appear to do their own, barely contained fourth of July impressions, I am also interested in this question. ---
**Author:** ![HongKongFooey](https://avatars.discourse-cdn.com/v4/letter/h/c4cdca/32.png) [@HongKongFooey](https://boards.straightdope.com/u/HongKongFooey)\ **Post date:** [September 26, 2008, 5:30pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/5 "2008-09-26T17:30:16Z")
> [@Interconnected\_Series\_of\_Tubes](#): > > Having purchased three inflatable beds in the last year and having noticed that _all three_ of the included electric pumps appear to do their own, barely contained fourth of July impressions, I am also interested in this question. Depending on the type of motor the sparking may be normal. Ideally there wouldn’t be any of course, but many universal motors spark a lot during normal operation. Makers of products like inflatable beds have a lot of incentive to keep their costs down as well as the size and bulk, I think the motor on the pump would be one of the main areas they could economize. ---
**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\ **Post date:** [September 26, 2008, 6:15pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/6 "2008-09-26T18:15:58Z")
> [@HongKongFooey](#): > > Are the ends of the brushes pitted? Are the springs or brush holders keeping them seated properly? How does the commutator surface look? There are a lot of reasons for a motor to spark. Can you see the electrodes when you look at the end of the brushes, sometimes even when they look like there is a lot left, they’ve worn down enough to expose the lead inside the brush (at least with larger motors I’ve seen that). The brushes look fine. They look clean at the ends, slightly curved from where they make contact. No signs of any rod. The springs are definitely pushing them in the right direction. The commutator is a dirty copper colour from the graphite debris. The entire armature is able to slide a centimeter or so back and forth. I assume this is normal. ---
**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\ **Post date:** [September 26, 2008, 6:16pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/7 "2008-09-26T18:16:59Z")
> [@HongKongFooey](#): > > Depending on the type of motor the sparking may be normal. Ideally there wouldn’t be any of course, but many universal motors spark a lot during normal operation. There is more than the usual small sparking. The fact that I smell something burning tells me not to continue. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [September 26, 2008, 6:46pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/8 "2008-09-26T18:46:45Z")
> [@solkoe](#): > > There is more than the usual small sparking. The fact that I smell something burning tells me not to continue. The excessive arcing may be due to high motor loading. It may be binding somewhere, or the bearings may be shot. Does it turn easily by hand? ---
**Author:** ![HongKongFooey](https://avatars.discourse-cdn.com/v4/letter/h/c4cdca/32.png) [@HongKongFooey](https://boards.straightdope.com/u/HongKongFooey)\ **Post date:** [September 26, 2008, 7:05pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/9 "2008-09-26T19:05:58Z")
> [@solkoe](#): > > There is more than the usual small sparking. The fact that I smell something burning tells me not to continue. Oh absolutely, heat and odor are sure signs of a problem in a motor. As **QED** suggests it sounds a lot like an overloading problem, possibly a bad bearing. I intended the sparking comment for **Interconnected Series of Tubes** , in my limited experience with those types of devices, the motors are set up to operate in forward or reverse (to inflate or deflate) so the brushes aren’t set up exactly in the neutral plane where there is no sparking for one direction because there would be excessive sparking in the reverse direction. They just set them up in a position to get the least sparking they can in either direction. ---
**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\ **Post date:** [September 26, 2008, 7:22pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/10 "2008-09-26T19:22:05Z")
> [@Q.E.D](#): > > The excessive arcing may be due to high motor loading. It may be binding somewhere, or the bearings may be shot. Does it turn easily by hand? Yes, it turns very easily by hand. After trying it again, there is a tremendous amount of arching come directly from the brush area. Also, an annoying squeal which leads to believe it is a friction problem. Quite a mystery. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [September 26, 2008, 9:10pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/11 "2008-09-26T21:10:57Z")
> [@solkoe](#): > > Yes, it turns very easily by hand. What about whatever it is the motor drives? Does _that_ also rotate freely? ---
**Author:** ![HongKongFooey](https://avatars.discourse-cdn.com/v4/letter/h/c4cdca/32.png) [@HongKongFooey](https://boards.straightdope.com/u/HongKongFooey)\ **Post date:** [September 26, 2008, 11:22pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/12 "2008-09-26T23:22:41Z")
> [@solkoe](#): > > Yes, it turns very easily by hand. After trying it again, there is a tremendous amount of arching come directly from the brush area. Also, an annoying squeal which leads to believe it is a friction problem. Quite a mystery. What you’re describing sounds very much like the brush holder has shifted, the entire assembly can be rotated relative to the stator. Armature reaction causes theses exact symptoms in DC motors, I’m not sure about universal motors which is probably what’s in your vacuum. In DC motors we usually just run the motor and shift the brush holder until the arcing is minimized, at least we used to - I haven’t seen a problem like that in a long time. Look at the assembly holding your brushes and see if it could have moved. ---
**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\ **Post date:** [September 26, 2008, 11:23pm UTC](https://boards.straightdope.com/t/electric-motor-sparking/465355/13 "2008-09-26T23:23:43Z")
> [@Q.E.D](#): > > What about whatever it is the motor drives? Does _that_ also rotate freely? The motor drives a fan (its a vacuum cleaner). I always assumed that the fan was turning too but I’ll check it out.