Broken Gear Teeth Cause Window to Only Go Down

You press the window switch and hear the motor whir, but the glass only goes down never back up. If this sounds familiar, there's a good chance the gear teeth inside your window regulator have stripped or broken. This is one of the most common mechanical failures in power window systems, and ignoring it can leave your car exposed to rain, theft, or a failed state inspection. Understanding what's happening inside the door panel saves you time, money, and the frustration of guessing at the wrong fix.

Why does my power window go down but not up?

When a power window moves in one direction only, most people assume the window motor is bad. That's a reasonable guess, but it's often wrong. In many cases, the motor itself is perfectly fine. The real problem is inside the window regulator assembly specifically, the small gear teeth that transfer the motor's rotation into the up-and-down movement of the glass.

Those gear teeth are usually made of plastic or a soft metal. Over time, repeated use wears them down. Once enough teeth strip or break, the gear can no longer grip in one direction. Since the motor still works, you'll hear it spinning when you press the switch, but the window won't follow. If you're unsure whether it's the motor or regulator causing the issue, our guide on how to tell if the window motor or regulator is bad walks through the differences step by step.

What exactly are "stripped gear teeth" in a window regulator?

Most power window regulators use a cable-driven or gear-driven mechanism. In gear-driven regulators, a small gear attached to the motor shaft meshes with a larger gear or a toothed track on the regulator arm. When you press the window switch, the motor turns this gear, which pushes the regulator arm up or down, moving the glass with it.

When the plastic gear teeth strip, the motor's gear can no longer grab onto the regulator gear in one direction. Here's why it often works down but not up:

Gravity assists the downward motion. The weight of the glass helps push it down, so even partially engaged teeth can carry the window down.
Going up fights gravity. The motor needs full gear engagement to lift the glass against its own weight. Stripped teeth simply can't hold that load.
Wear pattern matters. The teeth tend to wear unevenly. One side of the gear may be more damaged than the other, depending on the most common direction of use or the starting position of the window.

How can I confirm the regulator gear is the problem?

Before tearing into the door panel, run a few simple checks:

Listen to the motor. Press the up switch. If you hear the motor running but the window stays put, the motor is getting power and the switch is working. The break is mechanical, not electrical.
Try the "push and hold" method. Gently press or pull the window glass upward with one hand while pressing the up switch with the other. If the window catches and slowly rises with pressure, stripped gear teeth are almost certainly the cause. The extra force helps the remaining teeth grab.
Inspect for visible damage. Remove the inner door panel (usually held by a few screws and plastic clips) and look at the regulator assembly. Stripped gear teeth are often visible you'll see rounded, chipped, or missing teeth on the small drive gear.
Check for a manual override option. Some vehicles have a way to manually raise the window temporarily while you arrange a repair. Our article on manually overriding a stuck power window covers methods that work in an emergency.

Can I fix stripped gear teeth, or do I need to replace the whole regulator?

It depends on the design of your regulator. There are three common scenarios:

Replaceable gear kit (older vehicles). Some regulators use a separate drive gear that bolts onto the motor. You can buy just the gear for $5–$20 and swap it without replacing the whole assembly. This is the cheapest and easiest fix.
Integrated gear and motor assembly. Many modern vehicles combine the motor and gear into one unit. If the gear is built into the motor housing, you'll need to replace the motor assembly. Aftermarket motors typically cost $20–$60.
Full regulator replacement. If the regulator itself uses a cable-and-pulley system or the gear damage extends beyond the drive gear, replacing the full regulator assembly is the safest bet. Regulators run $30–$150 depending on the vehicle.

For a deeper look at mechanical regulator failures and what to expect during diagnosis, see our breakdown of broken gear teeth in power window regulators.

What are common mistakes people make with this repair?

Buying a new motor when the motor is fine. This wastes money and doesn't fix the problem. Always test the motor electrically before replacing it.
Using epoxy or glue on stripped teeth. Some forums suggest filling in missing teeth with epoxy putty. This might work for a few days, but the repair won't hold under the load of lifting the glass. It's a temporary bandage at best.
Forcing the window up by hand without disconnecting the motor. You can damage the motor's internal brushes or bend the regulator arms this way. If you need to move the glass manually, disconnect the motor connector first.
Skipping the door panel clip replacements. Those plastic clips break when you remove the panel. Buy a cheap assortment pack beforehand so your panel doesn't rattle after reassembly.
Not checking the window track and seal. Sometimes the regulator works fine, but a dry, warped, or pinched window seal creates so much friction that the weak gear can't push the glass up. A quick shot of silicone lubricant on the window channels can make a noticeable difference.

How much does it cost to fix a regulator with broken gear teeth?

Costs vary based on your vehicle and whether you do the work yourself:

DIY gear replacement: $5–$20 for the gear, about 1–2 hours of your time
DIY motor replacement: $20–$60 for the part, 1–2 hours
DIY full regulator replacement: $30–$150 for the part, 1–3 hours
Shop repair (full regulator): $150–$400 total, depending on labor rates and vehicle make

According to RepairPal's estimator, window regulator replacement labor typically ranges from $80–$180 in most markets. Luxury and European vehicles often cost more due to part prices and complex door assemblies.

Is it safe to drive with a window stuck down?

You can drive, but you're taking on real risks:

Weather exposure. Rain, snow, and even heavy dew can soak your interior, damage electronics, and cause mold.
Theft. An open window is an invitation. Even a partially open window is enough for someone to reach in.
Failed inspection. Many states require all windows to be operational for a safety or emissions inspection to pass.

If you can't fix it right away, use a heavy-duty trash bag or a purpose-made window cover as a temporary seal. Tape it securely around the outside of the frame with painter's tape (which won't damage paint) to keep moisture out until you can make the repair.

How do I prevent gear teeth from stripping again?

Avoid holding the switch after the window is fully open or closed. Hitting the end of travel puts maximum stress on the gear teeth. Let go of the switch as soon as the window stops moving.
Don't force a frozen window. If the glass is iced shut, defrost it first. Running the motor against a stuck window is the fastest way to strip the gears.
Lubricate the window tracks twice a year. A silicone-based spray on the rubber channels reduces friction and takes load off the regulator.
Replace worn regulators early. If your window starts moving slower than usual or makes a clicking or grinding noise, that's early warning of gear wear. Acting at this stage can prevent a full failure at the worst possible time.