MotionRebuild shelfTest and identify

Small pump

Also called drain pump, peristaltic, diaphragm pump, washer pump.

Appliance pumps are real pumps, usually at mains voltage. Inkjet peristaltic pumps are the low-voltage exception and are kind to whatever is in the tube.

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
Washer / dishwasher drain	Usually a small synchronous or shaded-pole motor, mains, not self-priming for a tall lift
Car washer pump	12 V DC, centrifugal, hates dry running
Inkjet peristaltic	Low-voltage DC, positive displacement, fine for dye and for metering
BP monitor	Tiny diaphragm pump, 3–6 V, low volume, made for air

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

Sump for a small tank
Coolant
Air bladder
Chemistry only if the wetted material survives the fluid

Leave this one when

The impeller is cracked or the peristaltic tube is flat. Tubes are a consumable.

Buying a new one is the better idea when

A documented 12 V pump if the salvage one is mains and you are building a battery system.

How to tell if this one still works

Nameplate voltage, a bucket, and a short run. Do not run a centrifugal pump dry while you look for the wires.

Tools you will want: Meter, Tubing.

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.
mains: Ordinary household wall power. It can kill. Unplug before you open anything that used it, and do not experiment on live wiring.
diaphragm: A flexible disc that moves with pressure or with a pump. In a washer it is how a small switch senses water level without the switch getting wet.

Where people actually find it

5 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	Prize	1–2	always	Bottom, drain pump.
Dishwasher	Prize	1–2	usually	Sump.
Blood-pressure monitor	Prize	1	usually	Inside.
Inkjet printer	Bonus	1	sometimes	Ink-system models.
End-of-life car	Bonus	1	usually	Washer bottle.

Prize — take this firstWashing machine1–2 · always
In this particular machine
Mains motor, small head. Some have a separate recirculation pump.
Where to look
Bottom, drain pump.
How to get it out
Have a pan. The volute will spill.
The condition to expect
Impellers crack; check them.
Prize — take this firstDishwasher1–2 · usually
In this particular machine
Circulation and drain. Mains.
Where to look
Sump.
How to get it out
It will be filthy. The seal is the usual failure.
The condition to expect
Impeller may be cracked.
Prize — take this firstBlood-pressure monitor1 · usually
In this particular machine
A 3–6 V diaphragm pump for air.
Where to look
Inside.
How to get it out
Keep the tubing.
The condition to expect
Good.
Bonus, if you are already in thereInkjet printer1 · sometimes
In this particular machine
A peristaltic pump for purging.
Where to look
Ink-system models.
How to get it out
The tube is often flat. The motor is the part.
The condition to expect
Tube is a consumable.
Bonus, if you are already in thereEnd-of-life car1 · usually
In this particular machine
12 V centrifugal.
Where to look
Washer bottle.
How to get it out
It hates being dry.
The condition to expect
Good.