#222 — Wiper Motor Rotisserie

Wiper motor's worm-geared slow spin + a spit rod = the laziest, most effective BBQ rotisserie ever built.

Ratings

🧪 What Is It?

A windshield wiper motor is a DC motor with an internal worm gear reduction that converts high-speed motor rotation into slow, high-torque output — typically 40-65 RPM. That's almost exactly what you need for a rotisserie spit. Commercial rotisserie motors cost $30-80 and do the same thing worse, because wiper motors are overbuilt to survive years of rain, snow, and ice loads on a windshield. Wire a wiper motor to a 12V battery (or a 12V wall adapter), attach a spit rod to the output shaft, and you have a rotisserie motor that will turn a whole chicken for hours without complaint. The worm gear is self-locking, meaning the weight of the food can't backdrive the motor — it holds position even when power is cut. This is the easiest, most useful junkyard build in the entire repo.

🔨 Build Steps

1. Pull the wiper motor. At the junkyard, unbolt the wiper motor from the firewall. Cut the wiring harness with a few inches of wire still attached. There are usually three wires: ground, low speed, and high speed. You only need ground and low speed for a smooth, slow rotation.
2. Test the motor. Connect 12V across the ground wire and the low-speed wire. The output shaft should turn slowly and steadily at about 40-50 RPM. If it's too fast, you can reduce the voltage with a simple voltage divider or PWM controller. Most wiper motors at 12V are already a perfect rotisserie speed.
3. Adapt the output shaft. The wiper motor's output is a splined or knurled shaft with a threaded tip (designed to hold the wiper arm). You need to connect the spit rod to this shaft. Options: drill a hole through the spit rod end and bolt it to the wiper arm mount, use a coupling nut, or weld a socket adapter to the shaft. The connection must be solid — a 5-pound chicken creates real torque.
4. Build the motor mount. Bend or weld an L-bracket from angle iron that bolts the motor to the side of your grill, smoker, or fire pit. The motor body should be outside the heat zone — wiper motors have plastic housings and internal grease that don't love sustained high temperatures. Keep the motor at least 12 inches from direct flame.
5. Install the spit rod and forks. Slide the spit rod through the motor adapter, through the grill/smoker, and rest the far end on a bearing or V-bracket support. Install spit forks on the rod to hold the meat. Tighten the fork thumbscrews so the food is centered on the rod's axis — off-center loads wobble and stall the motor.
6. Wire the switch. Install a toggle switch in-line with the positive wire between your 12V source and the motor. This lets you stop and start the rotation for loading and unloading food.
7. Cook. Load the food, balance it on the spit, turn on the motor, and let it spin. A whole chicken takes about 90 minutes over medium coals. The constant rotation bastes the meat in its own juices and produces an insanely even cook. The wiper motor won't care — it was designed to run for hours in a blizzard.

⚠️ Safety Notes

• Keep the motor body and wiring away from direct flame and high heat. The motor housing is often plastic and the internal grease is petroleum-based. Mount the motor outside the cooking zone with the spit rod extending into the heat area.
• If using a car battery as the power source, keep it away from the grill — batteries vent hydrogen gas when charging, which is flammable. A 12V wall adapter is safer for stationary setups.

🔗 See Also

• Scooter Motor Lathe
• Stirling Engine