MotionRebuild shelfUnplug and unscrew

Shaded-pole motor

Also called squirrel cage fan motor, C-frame motor.

The simplest AC motor: a squirrel cage and a copper shading ring that makes it start. Desk fans, bathroom fans, microwave stirrer fans, older fridge fans. Low torque, nearly immortal, inefficient.

If you are new to this category

These parts spin, push, or pump. A motor is a machine that turns electricity into turning. Some start turning as soon as you connect a battery. Others look identical and will not move until a small circuit tells them which coil to power next. The label, or the number of wires, is how you tell them apart.

Count the thick wires before you apply power. Two wires usually mean a brushed motor that can run from a battery. Three thick wires usually mean a brushless motor. Keep the board that came with a brushless motor.

A brushed motor

Two wires mean you can try a low, current-limited voltage and it should spin. The case often hides a label. If the only label you can find is on the machine, that voltage is the one to believe, not a hobby guess.

Mains voltage. Line voltage, and the DC bus just after the rectifier, both kill. A disconnected cord is not a discharged supply.

Specification. The right-hand column is what is typical. The label on the part in your hand wins if they disagree.
What to look for	Usual figure
Supply	Mains frequency. Speed is tied to line frequency and pole count, then slipped a little under load.
Start	No capacitor. Direction is fixed by which side the shading ring is on, unless there are two windings.
Torque	Poor. It will not drive a gearbox that a universal motor would.

Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.

What people actually use it for

Continuous low-power airflow
Teaching motor: you can see the entire magnetic circuit

Leave this one when

The bearings scream. That is why the fan was scrapped. A shaded-pole winding rarely 'burns out' before the sleeve bearing dies.

Buying a new one is the better idea when

If you wanted a quiet DC fan for an enclosure. A 12 V PC fan is the better part.

How to tell if this one still works

With the blades attached so it has airflow, a brief mains run. Smell and scream mean stop.

Step-by-step on the bench: Identify an unknown motor

Tools you will want: Meter, Insulated test leads.

Words on this page

Short meanings, so the rest of the entry is readable if you are not already doing this every weekend.

mains: Ordinary household wall power. It can kill. Unplug before you open anything that used it, and do not experiment on live wiring.
capacitor: A part that stores a small amount of electrical energy. Large ones in power supplies can stay charged after you unplug. Discharge them before you touch the leads.
torque: Twisting strength, as opposed to speed. A gearbox trades speed for torque. That is why a drill can turn a screw slowly with force.

Where people actually find it

4 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.

Harvest at a glance
From	Call	How many	How often	Where it sits
Desk or box fan	Prize	1	usually	The hub.
Microwave oven	Worth it	1	usually	Cooling the magnetron.
Refrigerator	Worth it	1–2	usually	Evaporator and condenser fans.
Space heater	Worth it	1	usually	The fan motor, when it is not a DC fan.

Prize — take this firstDesk or box fan1 · usually
In this particular machine
Mains, low torque, continuous duty. A C-frame or a unitized motor.
Where to look
The hub.
How to get it out
If it screams, the bearing is the scrap and the copper is scrap copper.
The condition to expect
Quiet ones are excellent.
Worth pullingMicrowave oven1 · usually
In this particular machine
A small mains fan.
Where to look
Cooling the magnetron.
How to get it out
Take it with the blade.
The condition to expect
Good if it spins freely.
Worth pullingRefrigerator1–2 · usually
In this particular machine
Small mains or DC fans, model depending.
Where to look
Evaporator and condenser fans.
How to get it out
The evaporator fan is behind the inside panel.
The condition to expect
Good.
Worth pullingSpace heater1 · usually
In this particular machine
Mains.
Where to look
The fan motor, when it is not a DC fan.
How to get it out
Spin by hand.
The condition to expect
Sleeve bearings fail.