vacuum cleaner puzzler.

Hi all,
got a real puzzler. Bought and old canister type vacuum off eBay and it arrived today. Hooked it up, started testing it out, seemed to work fine. Vacuumed the kitchen and dining room (tile floor) then got to an area rug in front of the sink. Switched to the power head and it worked OK for a minute or so and then tripped its built in circuit breaker. I noticed when it was operating that the light bulb flickered a little bit. Reset it, tried it again, same thing, but this time I grabbed the (steel) wand instead of the rubber coated end of the hose and got that unmistakeable tingle of AC. I whipped out my trusty Fluke and can't seem to find anything in the wand, hose, etc. where either of the power leads are shorting to steel; same thing with the body of the vacuum itself. I even metered between both prongs of the power cord to the vacuum case, still nothing. I *suspect* that the issue is with the power head, but there doesn't seem to be anything amiss there that I can identify with a meter - if nothing else, there's no way for even a short to the case to get to the wand, as there is no possible electrical connection between the body of the power head and the wand (the connecting piece is plastic.) The one thing I did not do was to hook up the power head and operate it and measure the voltage from the wand to a known ground; I didn't want to smoke the thing completely and then have the seller tell me that I damaged it.
I'm inclined to just box the whole thing up and send it back for a refund, but I'm quite honestly puzzled - can anyone come up with a reasonable explanation as to how this could happen, given what I saw with my meter above? This is really perturbing me, usually I can come up with a reasonable explanation as to why something failed the way it did, but I don't get this one.
To make matters weirder, the vacuum was plugged into a GFCI protected outlet and the GFCI didn't trip. Or can one still feel a tingle below the threshold fault current for a typical GFCI?
nate
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buffalo ny: your issue can be narrowed down if you can duplicate the problem in a different house. if you can not, the troubleshooting of all items between your shock and the service at the pole should begin. my mystery turned out to be a freezer leaking hot ac to electrify a wet bx cable in the floor joists and be connecting my electrified hand to a properly grounded metal cabinet of a different electrical device. think outside the (electrical) box sometimes to the wiring and its insulation.
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buffalobill wrote:

Interesting idea, but that isn't this issue - the vacuum does not have a grounding type plug/cord.
nate
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Nate Nagel wrote:

May have a wire hose stiffener 'slinky' embedded in the plastic. How is the wand head powered? Does it have an external cord or what?

Why not test it? It's already smoked. Since you said it worked for a minute or 2 then I would suspect an intermittent short. Which you may never be able to see on the meter.

A GFCI will only detect a current imbalance from hot to neutral. If you are NOT grounded and make a hot to neutral connection through your body then you will be shocked all day until you let go. In most cases this shock is unpleasant but not lethal as you are able to reflex and pull away and hopefully not fall off a ladder or something.
A GFCI is designed to trip when it detects that some or all of the current is not returning to the neutral. In most cases the current would be leaking to ground such as a grounded metal frame of an appliance. The GFCI will trip if you grab a hot wire and you are grounded in some way such as when you are also touching a metal pipe, duct or concrete floor. This prevents a severe, paralyzing and often fatal shock which can happen under these conditions.
In your case the vacuum is not grounded and you were not grounded so the GFCI did not, and should not trip even under short circuit conditions.
Kevin

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* It could be an intermittent problem such as cord with frayed insulation that only comes in contact with metal when twisted a certain way. I would just send it back and not waste time on it. Who knows what other problems may surface a few months from now.
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Nate Nagel wrote:

Static? Rubber belt on steel shaft(s)? MikeB
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A possibility is that the tingle was due to static electricity generated by the air flow, especially if the humidity was low. We had a system at work that pumped oil thru a vinyl hose and it would give you a pretty good jolt sometimes from the hose. That is why gasoline hoses are partially conductive.
Don Young
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