Question about liftmaster Chamberlain Garage Door Opener Transmitter 300MC

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I have a Automatic Doorman Model 455, problem is door goes down with no trouble, but lifting it goes about 10" and stops. I have changed the "V" belt, the problem still exists. I did an ampere draw test, amp draw should be around 4.5amps, when going down amp draw is 2.3 amps, when lifting the draw is 6.9 amps which is way too much. I think the problem after 22 years of no problem usage, the motor is weakening. What is diagnosis? Email- Thanks

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You are probably right about the motor going.Does it get to a point where the door stops and the motor is making a humming sound? If so the motor is going for sure...In the mean time to get you by,try putting more tension on the spring of your door to give the electric door opener a little extra help as its opening.

Posted on Jan 03, 2011

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Okay...upon further inspection, my left spring has broken in two. Going to call around for some quotes to replace the spring. Thanks for the suggestions.

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