Chamberlain Liftmaster series GDO, has been working just fine for 5 years. Suddenly it acts dead, as if no power. Remotes, inside hard wired control, nothing shows power, no light bulbs work. Pushing remote button or manual button unit 'clicks' but no action.
One door sensor light was out, thought that was bad, replaced that, so both lights have indicator, still no change. There were thunderstorms at the time, maybe power surge? Everything I find seems to point to replacing the logic board, but hate to spend $$ if it doesn't fix the problem.
I've unplugged the unit overnight to 'reset' no change. The 'learn' led flashed bright 5 times, that points to overheating.
This exact thing happened to me. (also after a power outage). It was the start capacitor. Finding out whether its the cap or the motor is pretty easy to check. First unplug the unit and take the cover off. Turn the shaft of the motor to make sure it is free. (if you cannot turn it, then the problem is the motor). If it does, then check the windings. Use a multimeter set to ohms (or continuity) and read red to white, blue to white and red to blue. You should get numbers (or a ringing sound if equipped), if you read OL, again the problem is the motor.
If all of that checks out, take a picture of how the wires were connected to the cap and label each one with tape. The cap is not polarized so there is no positive or negative terminal, however the two blue wires and the two red wires should be connected to the prongs of the same terminal.
Use a socket or flathead and loosen the strap, then pull the capacitor out. BE CAREFUL NOT TO LET THE TERMINALS TOUCH ANY METAL ON THE WAY OUT.
Now you have to discharge the cap. Using rubber gloves and an insulated screw driver, (or, you can REMOVE THE LEAD from the meter and use the metal lead tip) touch one terminal with the back side of the metal part of the lead or screwdriver, then touch the other side of the metal lead to the other terminal (connecting the two). You should get a spark. Do this 2-3 more times to make sure it is fully discharged. Once it does not spark anymore it is discharged.
The side of the cap reads 53-64 mfd, -40/+65
Now, connect the leads back to the meter. Set the meter to Ohms (omega symbol) or Farads (uf, mf, etc) and touch one terminal with the black/neg lead and the red/pos lead to the other terminal. The ohms/continuity should read numbers or ring. If you are using the farad (mf) setting, it should fall between the stated range (53-64 mf) or close to it. If it reads OL or much much higher than 64mf, the capacitor is fried and needs replaced. Got my new one for $26 including shipping.
Hope that helps!
Pull the logic board and check it for burnt or missing traces on the printed circuit. Thunderstorms love logic boards.
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