If you fix washers for a living, a motor tester box is one of the most valuable tools you can have on your bench. It lets you pull a Whirlpool direct-drive motor out of a machine, plug it into the box, and run it forward or reverse completely independent of the timer or anything else in the washer. That capability solves problems that come up again and again in the field — and does so faster than any other tool I own.
Watch the Demonstration
Why This Tool Earns Its Spot on Your Bench
Here are the situations where I reach for mine:
Draining a washer with a tub full of water. A machine on a service call is stalled mid-cycle with a full tub and the drain pump isn’t responding through normal controls. With the test box, you can pull the motor leads, hook the motor up, and run the motor in the drain direction to pump the tub out through the drain assembly — no bailing, no siphoning, no wet vac.
Confirming a “won’t spin” call is actually the motor. Hook the motor to the box, run it through forward and reverse, and you’ve isolated the motor in under a minute. If it runs fine on the box, you know the problem is somewhere else — timer, lid switch, or capacitor — and you’ve saved yourself parts money and a lot of time.
Testing for a bad capacitor. If you can run the motor on the box but not from the timer, then the capacitor on the machine is likely bad. Swap in a known-good cap and run it again. A weak capacitor will let the motor hum, struggle, or fail to start; a good one fires it right up. The difference is obvious within a few seconds.
Diagnosing wiring or windings. If a motor refuses to come up to speed even on the test box, sounds rough, or smells hot, the motor itself is bad — open windings, shorted windings, or burned insulation. You’ve isolated the failure without tearing the machine apart any further.
Repurposing a junked motor. Plenty of old direct-drive motors still have years of life left in them. A test box turns one into a benchtop motor you can wire to a grinding wheel, a bench fan, a small pump — whatever needs cheap, reliable rotary power.
This video covers the Whirlpool direct-drive box specifically. The newer Whirlpool and GE-style machines use a different motor architecture and need their own version of the tester. The GE-style build guide on Gumroad covers what you need — the newer Whirlpool box follows essentially the same design.
Safety Notes
This box exposes you to line voltage. Treat it that way:
- Always unplug from the wall before connecting or disconnecting a motor
- Never touch motor terminals while the box is plugged in
- Run on a GFCI-protected outlet
- Don’t run a motor for more than 15-20 seconds at a time on the bench unless it’s fastened down
- Keep the switch in the OFF position when you’re plugging or unplugging
What You Need
- Fluke 101 Digital Multimeter — Search on Amazon
- Whirlpool Washer Motor Capacitor (for swap testing) — Search on Amazon
Building your own? The complete parts list — every switch, capacitor, terminal, grommet, and length of wire — is in the Gumroad guides linked at the bottom of this post: Whirlpool direct-drive and newer GE-style.
Disclosure: As an Amazon Associate, I earn from qualifying purchases made through the links in this post. It costs you nothing extra and helps support the channel.
Want to build your own? I have step-by-step guides on Gumroad with the wiring diagrams, parts lists, and full build walkthroughs — one for the Whirlpool direct-drive box (https://harperknowles.gumroad.com/l/ywmqhp) and a separate one for the newer GE-style machines (https://harperknowles.gumroad.com/l/yxuxno). Browse all my repair guides at https://harperknowles.gumroad.com.
Rather have a pro do it? If you’re anywhere in central Louisiana — Oakdale, Oberlin, Elizabeth, Pitkin, Pine Prairie, and Glenmora — Harper & Knowles handles this all the time. Call (337) 831-6757 or visit harperandknowles.com to schedule a service call.
About the Author: Chip Knowles owns Harper & Knowles Washing Machine and Dryer Repair LLC in Oakdale, Louisiana. New video every Sunday at 2 PM Central on YouTube.