Garage door opener capacitor selection - Page 1
Forum section: electronics / projects

author: kw012
author_rank: Newbie
timestamp: March 25, 2025, 04:25:37 pm
content: A few days ago I purchased a New Old Stock opener, unopened in the box from FB Marketplace seller. 2008 Liftmaster. After installation I tested it and it ran maybe 5 seconds, stopped, all power shut down on the unit, wall switch and reverse sensors. Then after maybe 10 seconds, powered back up. Then it ran for at least 7 cycles while I adjusted the distance limiters. The next day it acted up again the same way. I am sure it has to be the capacitor. Calling Liftmaster determined that the exact cap is not available. The existing properties on the orig cap show 56uF, 250VAC. In discussion with their limited tech support, I got hung up on my lack of understanding...Their suggested replacement spec showed 220V. My house does not run 220V, it runs 120V like everyone else. Their replacement, like my original, shows 250VAC on the cap that they say has 120V properties. It is a bit larger and has 89uF on the label. Also shows 250VAC on the label. They also offer a 53uF-64uF 220V cap showing 250V on the label. Searching elsewhere I found a cap from the same manufacturer and it shows 56uF 220V with that 250VAC on the label as well. I think this might be the best one. Any thoughts are appreciated, my friends. I am only versed in the specs for my HVAC system caps, and this is new to me. TY in advance for your thoughts. Keith

author: TimFox
author_rank: Super Contributor
timestamp: March 25, 2025, 04:28:32 pm
content: The voltage rating on such capacitors is amaximumvalue for safe operation, not a recommended operating condition.

author: Peabody
author_rank: Super Contributor
timestamp: March 25, 2025, 05:50:32 pm
content: The last time I replaced the capacitor in my ancient Sears opener, I got a run capacitor from Grainger having the same value. The original and all subsequent capacitors were start capacitors. I think run capacitors should last longer than start capacitors. But they are more expensive. Maybe someone who knows motors can comment on whether I did the right thing.

author: floobydust
author_rank: Super Contributor
timestamp: March 25, 2025, 06:23:22 pm
content: Welcome to the forumsWhat model is this?There are capacitors on the control board, the obstacle sensors, and the motor.You are assuming it's the motor cap - but that's not the problem, it won't cause a "power shut down". If the motor run cap is bad, the motor will have weak torque or not move.Make sure the wiring to the wall switch and obstacle sensors is not getting crushed or shorting out or a bad connection. If the opener is not connected to the obstacle sensors it will not operate.Depending on the model, they sorta do this:If, while closing, it auto-reverses to full open, and the opener lights flash X times, then it's the obstacle sensor that caused it.If, while closing, it stops and the opener lights flash Z times, then it's tripped on high torque as it squishes the cat.There are problems and productrecallsover the newer (2022) myQ garage door wall control panels. Bad supercapacitor.

author: wraper
author_rank: Unknown
timestamp: March 25, 2025, 06:39:00 pm
content: QuoteThat's what you should be using. Whoever suggested 89uF is an idiot.

author: CaptDon
author_rank: Super Contributor
timestamp: March 27, 2025, 10:52:39 pm
content: If you don't understand the ability to use 220VAC / 250VAC capacitors on a 120VAC motor you are not 'well versed' in HVAC since you often see the same exact thing with 120VAC air handling motors and sometimes also on refrigerators, dehumidifiers and small 120VAC window air conditioners.