Symptoms
- Motor hums or runs but door stays still
- Trolley carriage may be visibly separated from the door arm
- Chain or belt may look loose or broken
Likely causes
- CommonEmergency release engaged, disconnecting the trolleyThe release cord is designed to disconnect the door for manual operation, and it can be pulled accidentally.
- CommonBroken or badly worn drive chain, belt, or screwThe drive mechanism can wear out, strip, or snap after years of use.
- PossibleStripped plastic gear inside the opener motor unitThis is a very common opener failure point after years of regular use.
- PossibleBroken trolley carriage or armPlastic components connecting the trolley to the door can crack over time.
What to do
- Check the emergency release cord and mechanism to confirm the trolley is properly engaged with the rail, not disconnected.
- Look along the length of the rail for a visibly loose, sagging, or broken chain or belt.
- Listen closely to the motor; a whining or grinding sound without door movement often indicates a stripped internal gear.
- Check the trolley carriage where it connects to the door's arm for visible cracks or separation.
- If the drive chain or belt is broken, do not attempt to operate the door until it's replaced.
- For a suspected stripped gear, this typically requires opening the motor unit, which is often more practical to have done professionally given the low cost of opener gear kits versus labor.
Tools and parts
- Flashlight
- Ladder
Garage door opener gear and sprocket kitSearch: “garage door opener drive gear kit”
Replacement drive chain or beltSearch: “garage door opener replacement chain or belt”
When to call a pro
Call a garage door technician if the drive chain/belt is broken or you suspect a stripped internal gear and aren't comfortable opening the motor housing.
Safety
Use caution
Unplug the opener before doing any inspection or repair near the motor unit or drive mechanism.