MotionRebuild shelfTest and identify

Single-phase induction motor

Also called PSC motor, split-phase, washer motor, pump motor.

The workhorse in washers, dryers, furnace blowers, and larger fans. Often needs a start or run capacitor. The capacitor value is printed on the old can; do not guess it.

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	120 V or 230 V AC, nameplate
Capacitor	Run caps are tens of µF, motor-rated (not a DC electrolytic), often 370–440 VAC
Speed	Slightly under 1500 or 3000 RPM at 50 Hz, 1800 or 3600 at 60 Hz, for 4-pole and 2-pole
Rotation	Swap the start winding or follow the diagram on the plate. Do not swap random wires.

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

Anything that must run for hours
Blower, small lathe, buffer, if the power and speed match

Leave this one when

The motor came off a modern direct-drive washer. That one is a BLDC married to an inverter board, not this part.

Buying a new one is the better idea when

When you need a known horsepower and a face mount. Salvage frame sizes are whatever the washer needed.

How to tell if this one still works

Spin by hand. Check winding resistance and insulation to the frame. Replace a bulged run capacitor rather than starting the motor without one.

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

Tools you will want: Meter, Correct run capacitor.

Words on this page

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

nameplate: The printed label on the part or the machine. If the label and this index disagree, use the label.
BLDC: Short for brushless DC motor. See brushless. The 'DC' does not mean you can hook it to a battery with two wires.
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.
electrolytic: A common type of capacitor with a polarity. The stripe marks the negative lead. A bulging top means it has failed.
RPM: Revolutions per minute. How fast the shaft turns. A microwave turntable motor is a few RPM. A blender motor is many thousands.

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
Washing machine	Worth it	1	sometimes	Belt-drive machines.
Clothes dryer	Worth it	1	usually	Blower and drum drive.
Window air conditioner	Worth it	2	usually	Blower and condenser fan.
Garage door opener	Worth it	1	usually	The head.

Worth pullingWashing machine1 · sometimes
In this particular machine
Mains induction or a universal, with a belt.
Where to look
Belt-drive machines.
How to get it out
Read the plate. This is not the direct-drive motor.
The condition to expect
Good if it spins by hand.
Worth pullingClothes dryer1 · usually
In this particular machine
Mains motor, often with a centrifugal start switch.
Where to look
Blower and drum drive.
How to get it out
Read the plate. Do not drop it; the switch is glass-fragile on some.
The condition to expect
Good.
Worth pullingWindow air conditioner2 · usually
In this particular machine
PSC motors that need that capacitor.
Where to look
Blower and condenser fan.
How to get it out
Label which wires were on which capacitor terminal.
The condition to expect
Good if the original fault was the cap.
Worth pullingGarage door opener1 · usually
In this particular machine
Or a DC motor with a board, on later openers. Mains either way at the cord.
Where to look
The head.
How to get it out
Read the plate.
The condition to expect
Good.