Electric Motor Problem


I noticed that our central vac didn't sound right today. I took the plastic housing off the top of the motor so the commutator and brushes were visible and started it up. After a few seconds of operation I start to see the blue spark between the brushes and commutator start to extend almost 1/2" in the direction of rotation around the commutator. As this happens the speed of the motor slowly begins to drop. The motor was overhauled last April; new bearings and brushes.The vacuum is 22 yrs old so the commutator on the motor has seen a lot of wear but it looks in reasonable shape. Anybody have an idea what might be happening here? Thanks, Mike
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snipped-for-privacy@-NOSPAM-yahoo.com wrote:

You might need to clean out the slots on the commutator Also, make sure the brushes are the correct ones and have proper tension. Eric
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They used to say to "undercut the mica". Does that still apply? Did the overhauler do that last April? The mica is the stuff between the copper segments. When the copper wears down, the mica has to be cut down, I guess.

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Adding to Eric's commen\\ts, the overhaul should also have included truing and smoothing the commutator. My bet is on wrong brush type for the unit. Central vacs are robust machines that can draw considerable current and require a high conductivity brush and maximum commutator contact. The proper brush may even need considerable copper content like those in auto starter motors. A set of OEM brushes might help the problem. HTH
Joe
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Sounds like the brush springs are weak.
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Steve Barker


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22 years old? Buy a new vacuum cleaner.
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It's a central vac, not a $69 special. No reason not to fix it.
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Well, maybe there is a reason to replace it. He already spent time and money having the motor rebuilt less than a year ago. I guess I'd first take it back to whoever rebuilt the motor and ask them what's wrong. If I didn't get a convincing explanation, or it was going to cost much more to fix again, I'd be looking at a new one. You can get one for $250+
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snipped-for-privacy@optonline.net wrote:

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"One?" If that means a new re-builder, I guess I'd agree.
You can

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snipped-for-privacy@-NOSPAM-yahoo.com wrote:

It sounds to me like whoever did the overhaul used the wrong brushes. They're probably shedding carbon.
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Thanks to all who responded to my original post. I've taken a good look at the commutator on the motor and it doesn't look in the best of shape. I think the heat and arcing has pitted it badly. Guess I will look at replacing the motor. Apparently a replacement Lamb motor runs $195 to $245 here in Canada. Thanks, Mike

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Well I took the central vac into the dealer this morning so he could make sure I was getting the correct replacement motor. Of course he wanted to try it, to see what was wrong. After seeing it run for 15 secs he stopped it , went to the back of his shop and came back with a gray stick of some type of abrasive material. He started up the vacuum, held the stick in some needle nose pliers and ran it up and down the commutator a few times, removed the stick and let the vacuum run. The severe arcing had disappeared and he pronounced it good for another 5 years! He said this stick was the best thing for removing any carbon buildup between the commutator and also for removing any rough spots. It was about $10 CDN per stick. Sorry but I've forgotten the name ot it already ( CRS disease). Of course while there my wife spotted the new type of electrified hose with on/off switch on the handle and wanted one, ( doesn't like my duct tape repair on the old one ) so the guy was happy to not charge for the work and we came away with a little extra on our Visa bill! Mike
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Well I took the central vac into the dealer this morning so he could make sure I was getting the correct replacement motor. Of course he wanted to try it, to see what was wrong. After seeing it run for 15 secs he stopped it , went to the back of his shop and came back with a gray stick of some type of abrasive material. He started up the vacuum, held the stick in some needle nose pliers and ran it up and down the commutator a few times, removed the stick and let the vacuum run. The severe arcing had disappeared and he pronounced it good for another 5 years! He said this stick was the best thing for removing any carbon buildup between the commutator and also for removing any rough spots. It was about $10 CDN per stick. Sorry but I've forgotten the name ot it already ( CRS disease). Of course while there my wife spotted the new type of electrified hose with on/off switch on the handle and wanted one, ( doesn't like my duct tape repair on the old one ) so the guy was happy to not charge for the work and we came away with a little extra on our Visa bill!
Mike
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