How to Fix a Broken Window Crank Mechanism

Most window crank problems stem from stripped gears, worn springs, or broken handles that can be fixed by disassembling the mechanism, cleaning components, and replacing damaged parts.

1. Disconnect the Handle First. Look for a setscrew on the side of the handle or underneath. Remove this screw with an Allen wrench or screwdriver, then pull the handle straight off the shaft. Some handles simply pull off without a screw. If the handle spins freely without moving the window, the internal gears are likely stripped.
2. Expose the Housing. Remove the window trim around the crank area using a putty knife or pry bar. You'll see the metal housing that contains the gears and spring mechanism. Remove the screws holding this housing to the window frame and carefully pull it out.
3. Spot the Damage Inside. Open the housing by removing its cover screws. Inside you'll find gears, springs, and connecting arms. Check for stripped plastic gears, broken springs, or bent connecting rods. Clean all parts with degreaser and a wire brush to remove old grease and debris.
4. Swap Out Bad Parts. Take photos of the assembly before removing parts. Replace any stripped gears, broken springs, or damaged connecting arms with exact replacements from a hardware store or window parts supplier. Most mechanisms use standard parts that interchange between manufacturers.
5. Grease and Rebuild. Apply white lithium grease to all moving parts and gear teeth. Reassemble the mechanism in reverse order, ensuring all springs and gears align properly. The connecting arm should move smoothly through its full range of motion.
6. Verify Before Final Install. Before reinstalling, test the mechanism by hand to ensure smooth operation. Mount the housing back in the window frame, replace the trim, and reattach the handle. Test the window through several open and close cycles to verify proper operation.