How to replace a garage-door opener motor capacitor

Diagnose first

Symptoms of a failing opener capacitor: the door opens slowly, the motor “groans” or hums before catching, the door stalls partway and reverses, or the motor hums but the door won’t lift at all.

Opener motors use one of two kinds of capacitor, and which one yours has depends on the motor, not on the door:

• A run capacitor: a film capacitor, often a cylindrical CBB60 can, printed with a single µF value and a voltage rating (for example 450VAC).
• A start capacitor: an electrolytic capacitor, often a CD60 can, printed with a much larger µF value (frequently as a range) and its own voltage rating.

The label on your old capacitor tells you which one you have and the exact value. Read it before you order anything - don’t go by the opener’s model name or a “typical” value from the internet.

What you’ll need

• The replacement capacitor: the same type (run or start, same body code as the old one), the same µF (within the tolerance printed on it), and an equal or higher voltage rating.
• Stepladder you can stand on safely while working overhead.
• Phillips screwdriver.
• Insulated screwdriver for discharge.
• Phone for wiring photos.

If your old capacitor’s label says 6µF, 7µF, 8µF or 10µF and it’s a run capacitor rated 450VAC or lower, our CBB60 run capacitors in those values match it on µF and voltage: 6µF, 7µF, 8µF or 10µF. Check the terminal style and that the can fits the housing. If your label shows a different value, match that value instead. If it’s an electrolytic start capacitor, our guide to motor start capacitors (CD60) explains how to match its printed range.

Steps

1. Disconnect the opener from mains

Unplug at the wall outlet (most NZ openers plug into a ceiling-mounted 10A socket). Don’t just rely on the remote being off.

2. Release the door

Pull the emergency release cord (red handle on the trolley). This disengages the door from the opener so you can work without the door coming down on you if something accidentally fires.

3. Open the motor housing

Usually 4-6 Phillips screws on the bottom or end panel of the opener body. The capacitor is the cylindrical can with two wire terminals, usually clipped to the inside wall of the housing.

4. Discharge

Bridge the terminals with an insulated screwdriver for 10 seconds. A capacitor can hold a charge after the power is off, and start capacitors in particular can hold a lot. Be deliberate about discharging.

5. Photograph, then swap

Photo the wiring. Pull the spades, undo the clip, lift the cap out. Drop the new one in, re-clip, reconnect spades to the same terminals.

6. Close up and re-engage

Housing back on. Re-engage the trolley by lifting the door slightly until the latch catches (or by running the opener once with the door released, then re-engaging). Plug back in.

7. Test cycle

Run the door through one full open + one full close from the wall button (not the remote). Listen for a clean start: no groan, no hum, no stalling. Watch the door speed: should be the same speed it was when the opener was new.

Common gotchas

• Start vs run. A start capacitor and a run capacitor are different parts, even when the numbers look close. Replace like with like: same body code, same µF, same or higher voltage. Our run vs start capacitor explainer shows how to tell them apart.
• Wrong µF kills the opener. Too low and the motor won’t catch. Too high and the motor runs hot and the cap shorts. Match exactly.
• Heavy timber doors work the opener harder; if the cap is the second one to fail in a year, the opener is probably underspec’d for the door weight.

If the door still won’t lift after a clean cap swap, the next suspect is the trolley/chain drive (worn out or misadjusted), then the motor brushes (on older units). A replacement opener costs many times more than a capacitor, so the cap swap is the cheapest first try.