Shop-Vac....why did it quit working?

[JDgreen227]

My dad in law has a 5.5 hp 14-gallon Shop-Vac that quit working and I told him I would try to fix it. The switch gets power, the two red (hot) leads from the switch to the motor get current, the brushes are in good shape, the motor itself looks reasonably clean and doesn't appear to have been overheated. It also spins freely when turned by hand and I can find no loose or poorly crimped or soldered connections on the motor so the only cause I can think of is the possibility of a broken motor winding. Is there any way to check for that? Thanks.

Of course you cannot buy a new motor for the device, the alternative is to buy the complete powerhead which basically costs as much as the vacuum did brand new with all accessories.

 

[ustmd]

You look like you got all of the obvious ones...Did you check the neutral return? Electrons don't like to go out if they can't get home again.

 

[JDgreen227]

You look like you got all of the obvious ones...Did you check the neutral return? Electrons don't like to go out if they can't get home again.

You guys will not believe what the cause was !!! Atop the motor case itself, one of the red leads is attached to a spade terminal that goes into a square black block, and one of the bare wires that was wound around the stationary part of the motor (called a stator?) also was connected to a spade terminal that went into the square black block. The block is shown at the bottom left of the attachment with the spade terminal sticking out. Inside the black block are two small 90 degree shaped chrome springs that retain the spade terminals AND a tiny fusible link that had been melted. Connecting the red lead to the bare wire and bypassing the melted fusible link made the motor operational. From what I read online, the purpose of the fusible link is to shut down the flow of electricity in case the motor begins to overheat (from a clogged filter or whatever).

I have no idea if the tiny fusible link is even available as a service part but I connected the red lead to the bare wire with a solderless connection and told my dad in law NOT to let the filter get clogged or without the fusible link the motor may overheat and begin a plastic fueled fire.

Just wanted to pass this info along...a $100 shop vacuum rendered useless because of a 10 cent part....!!! You can see the second spade terminal with a temporary connection to the bare lead in front of the threaded motor shaft end.

 

[flyerdan]

You could wire in one of those after market inline auto fuse things that take a spade fuse. Put in a 5 or 7.5 amp or whatever the motor draws, will be less than the 15 amp breaker. Might not be ideal, but it does offer some overload protection.

 

[JDgreen227]

You could wire in one of those after market inline auto fuse things that take a spade fuse. Put in a 5 or 7.5 amp or whatever the motor draws, will be less than the 15 amp breaker. Might not be ideal, but it does offer some overload protection.

That is an excellent idea and the vacuum is labeled 11.5 amps...not sure if they make a fuse size close to that other than 10&15 but will check. What surprises me is that the bare wire going to the stator is only 20 gage...you would think that would have fried long before the fusible link would blow.

 

[clemsonfor]

I bet you can get a link online, or at radio shack. When i worked at an auto parts store we even sold fuesable links there, but were probly wired for way more current than that one was. I also thought a fuesable link would interrupt current flow but when colled would reconnect itself, thus not haveing to replace fuses each time overdraw situation was experienced? I guess this one failed?

 

[JDgreen227]

I bet you can get a link online, or at radio shack. When i worked at an auto parts store we even sold fuesable links there, but were probly wired for way more current than that one was. I also thought a fuesable link would interrupt current flow but when colled would reconnect itself, thus not haveing to replace fuses each time overdraw situation was experienced? I guess this one failed?

The "link" in this situation was simply a strip of metal about the diameter of a paper clip and about 3/8" long...I may be wrong but have always though fusible links were a one-time connection and had to be replaced once they are blown. Usually they are 4 wire gages smaller than the wire they are meant to protect(example: protect 12 gage wire with a 16 gage link) ...as I noted in an earlier post one of the wires on the vac motor was 16 gage and the other was 20 gage...not sure what size the link was but the hole appeared to be about 18 gage.

 

[clemsonfor]

Well i dunno, im probly wrong.

 

[KYErik]

The fusible link was likely designed to melt when the motor overheated. Replacing it with a fuse would offer protection from high current draw, but not overheating.

If it was mine, I'd temporarily bypass the fusible link and test run it for 5-10 minutes while feeling of the motor vent to see if it gets hot. After you verify that the motor isn't getting hot (from bad windings etc) then you could look for one of those fusible links to replace the burned out one.

You could try looking at hair dryer parts for something to replace that fusible link. My wife's blow drier has a little self resetting overtemp protector. When the air intake gets so clogged that it can't move enough air through it to stay cool, it disconnects power to the heating coils and you can hear the motor speed up.

 

[BigBoyinMS]

Fuse link wire is available at most any auto parts store. Or like was said earlier get an inline fuse holder with a 15a fuse.

edit: here ya go... Sealed Fuse Holders | Autofuse Fuse Holder | Mini Fuse Holders | White Products Cleveland Ohio Looks like they size fuse wire by size, not amperage. I've seen them at parts stores but a real electronics store would be better. Even a fake electronics store like Radio Shack might have them! :laughing: