Outside AC unit makes weird noise at start-sometimes!

My outside AC unit sometimes makes a loud vibrating sound for a few seconds when it starts-up. This only happens occasionally,but seems to be getting more frequent,Other than that,it seems to be working ok. What could be the cause? Start capacitor going bad? Where to buy? How hard to replace? I am a retired electronic tech. but am not familiar with AC service. Any help or suggestions would be appreciated! Thanx!
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Lee Baker wrote:

Mine did the same thing this spring. Sounded like a very rapid relay chattering. Repeated tries = same thing. Called service tech. Of course as soon as he tried, it worked. No more problems all summer and no, he had no suggestions as to what it was.
Harry K
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"Technician syndrome". when the techie is present, the problem doesn't occur. Same thing happens with photo copiers.
--

Christopher A. Young
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Lee Baker writes:

A failing contactor can chatter.
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could there be some debris such as leaves, twigs or paper inside the unit?
~~Phil~~
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On 17 Sep 2005 14:55:22 GMT, snipped-for-privacy@yahoo.com(Phil Marshall) wrote:

No I cleaned it out this spring and always keep the area around it clean as well. First started hearing the noise about 2 years ago,but seldom happened back then but receantly is happ more frequent. Unit is about 16 year old YORK. Thanx for replies
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wrote:

Well, THAT'S your problem! It's a damn YORK!!!!!!
;-]
(That was for The Breeze Man....)
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This is Turtle.
When I get a Call for Vibration of a condenser unit here is what I look for first.
***Fan blade with small crack in it or fan blade loose on motor shaft.
***Condenser unit not sitting level and will wiggle when it cranks.
***Some of the Screws missing out of the unit.
***The top bearing on the motor are going bad.
Here is a start of a looking list.
TURTLE
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On Sat, 17 Sep 2005 22:21:07 -0500, "TURTLE"

Thanks for your help TURTLE. Will check out the items that you list.Also thanks to all the others who took the time to respond!
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