I need to replace a brush to operate the shop vac. Where can I find it?

A lot of shop vac motors have brushes, due to the motor's power needs. Unplug it (obv) and get to taking off all the covers until it's just you and the motor. On most shop vacs, you shouldn't need to remove the impeller (fan), and it's better just left alone. The brushes are usually just under spring tension.

Is this on a Hoover SpinScrub by chance? If so, those brushes are driven by an air powered turbine. If that turbine isn't turning it may need to be replaced. They can be disassembled and oiled/greased but something like that is better left to a vac shop.

It may just be the fan slowing down and acting like a siren, or it may be a dry bearing. Take it all apart, clean and lubricate. Replace the carbon brushes perhaps whilst you are in there.

you can get them off the link below
http://store.advancecarbon.com/prostores/servlet/Categories

Most vacuum motor brushes are not serviceable by the consumer. without further information, I would take it to a vac shop for service. If you are mechanicaly inclined, take the motor out and then take the motor to a vac shop for service.

I’m happy to assist further over the phone at https://www.6ya.com/expert/robert_b96ba3f038cf317c

Detach the vac itself from low voltage thin wiring leading to the house. With the vac plugged into power, try the manual switch and then try shorting across the low voltage exterior terminals with a rubber gripped set of pliers.
If you can hear a clicking inside, this is the vac's relay trying to start the motor. If the vac is more than 5 years old , or used more than 2 hours a week, you may need new carbon brushes, or a motor overhaul or replacement depending on wear. Carbon brushes are specific to the motor model # inside the vac, most often an AMTEK Lamb motor.
If you need brushes, the motors comutator should also be inspected for excess,wear, like gap ing between its conatct segments and "apple core" shaped wear
.
You you have a meter and can test for continuity across the motor leads, do so and post back.

If you don't have a meter, you will likely want to lift the vac off the wall after these checks and take to a repair shop, saving $$$$ for a house call...

It sounds like you have bad carbon brushes on the motor. Get replacement brushes from a local vac shop, and take the unit apart. On each side of the motor their is a retangular piece of plastic with what looks like magnets in them. In most cases they are simply held by 2 screws. Replace these brushes and reasemble the unit. If the problem persists you have burned out the comutator on the motor and the whole thing must be replaced.

where can i fine moter brushes for my ridgid 5.25 hp 16 gal. wet dry vac.

If you remove the motor, you will see that the wires that go from the switch to the brushes. On one side there is one wire connected directly to the brush. On the other side the wire goes to a plastic plug with a second wire going to the brush. This is probably where the problem is. This is a fusible link and it has most likely melted creating an open in the circuit. I put a piece of solder where the link was and the motor ran BUT the brushed arced like a sparkler. Upon further examination the brushes were crumbling apart. I have been unable to find replacement brushes.
This machine has a five year warranty. I called Shop Vac Customer Service 1-888-822-4644 and they sent me a new motor.
I had a Shop Vac QL50EIC which had exactly the same problem but the warranty was expired so that I had to buy another motor for about $50.

I'm afraid you'll need to take it apart. the switch is mounted in a plastic holder in the top. While you got it apart and without it plugged in, check to see that both brushes are touching the commutator. there should be sufficient spring tension to hold the brushes against the spinning part [commutator] if even one brush isn't making contact it won't spin.