Buzzing from outside AC unit - outside fan is running

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Hi - we have a typical home AC system - ours is a Ruud - the model number on the outside unit is UAKA- 037JAZ. It's been very hot here in Texas - over 100 all day long, but the system is working OK and cooling the house - plenty of cool air coming out of all the vents - the AC runs a lot these days, but it always has when it's very hot outside since we've lived here - I guess that's because it's an older unit (1996) and not as efficient as some of the newer units. The filter has always been changed regularly.
For several months now, I'm hearing a loud buzzing noise from the outside unit when it's running - the fan spins OK and there's hot air coming off of the unit - the noise is nothing that keeps us awake at night, but certainly noiser than my neighbor's units - they were replaced within the past few years and they're newer.
Is this kind of noise typical of the older units?? If not, what am I likely to hear is the main problem from the AC repair guy if the unit goes out and I need to make a repair call?
I had something on the outside unity replaced a few years ago - I think it was the start capacitor.
Thanks!
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What you are hearing is the relay , or contactor,inside the condenser. It receives 24 volts from the blower unit, which energizes it's coil, pulling in the relay,sending 240 volts to the condenser motor . When these relays get old or worn, then start making humming or buzzing noises. It's not an expensive part and with limited electrical experience, can be changed by a homeowner.

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Thanks RBM - "It is not an expensive part" is excellent news!
"with limited electrical experience" - I've never electrocuted myself - I guess that qualifies my experience as limited, but I think I'll call a repair guy to do the work anyway.
Much appreciated!
Joe
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For most people, calling the professionals is advisable. Here is a link to a typical condenser contactor. It is a double pole relay with a 24 volt electromagnetic coil: http://www.ecrater.com/p/6264911/24-volt-2-pole-a-c-contactor-air-conditioning #

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I agree with calling a professional. Limited electrical experience aside, limited AC experience might lead to enough confusion to cause problems. It is good to knkow the likely problem, though, so it can be priced out, and to avoid the laundry list of possible expensive fixes.
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wrote:

I agree with calling a professional. Limited electrical experience aside, limited AC experience might lead to enough confusion to cause problems. It is good to knkow the likely problem, though, so it can be priced out, and to avoid the laundry list of possible expensive fixes.
Absolutely - I didn't wanna have a guy come by and tell me "contactor" and give me a bill for $500. The part is around $30 - with labor, I'm thinking that the total should be around $100.
Thanks again, guys!
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Fair retail price, too. Many AC units use single pole contactor. For when the unit has a crankcase heater.
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While the repair guy is at your home. Please ask him to clean the condensor. He should spray on some chemical, onto the outdoor radiator grille. This will foam up after a minute or two. He should rinse it all off with a garden hose, and might need a second or third cleaning. Cleaning the condensor will help with efficiency, and lower your energy bill.
Do this after replacing the conactor, so he's not kneeling in water.
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I've actually cleaned the condensor coils myself - I took apart the sheet metal pieces surrounding the coils and hosed them off real good - I think I actually sprayed some kitchen cleaner \ degreaser on the coils after I hosed them off the first time, and then after spraying them down with the cleanser, hosed them off again. When I started, there was an unbelievable amount of grass clippings and other, accumulated gunk in the coils.
Thanks for the suggestion !!
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On 7/18/2010 5:15 PM, AngryOldWhiteGuy wrote:

Most home owners don't realize that they must turn off the AC when cutting the grass. The condensing (outdoor) unit is like a giant vacuum cleaner and will inhale a lot of dirt and dust. I always try to get customers to cut back the hedges from the unit and lay a bed of pea gravel around the base of the unit and keep the pine straw and other landscape fill away from the condenser.
TDD
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On Sun, 18 Jul 2010 14:15:29 -0500, "AngryOldWhiteGuy"

That qualifies my experience as limited, you say.
Even more limited than if you had electrocuted yourself.
Now that would have been an experience

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RBM wrote:

In my experience, when the relay is located outdoors and not well sealed from the environment, what happens is that the D shaped copper "shading coil" at the armkature end of the relay coil corrodes into nothingness and can no longer serve its function of creating an out of phase AC magnetic field to prevent the buzzing of the relay armature.
(More than you needed to know, huh?)
Jeff
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On Jul 18, 12:03pm, "AngryOldWhiteGuy"

When was the last time anyone lubricated your condenser fan motor?
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wrote:

When was the last time anyone lubricated your condenser fan motor?
Probably when it was built, and sealed at the factory
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Last time mine buzzed I just tightened the loose screws on the housing and everything was quiet again. That was about 10 years ago - the AC is about 35 years old.
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On Sun, 18 Jul 2010 20:03:34 -0400, snipped-for-privacy@snyder.on.ca wrote:

It's not the fan motor. Even if it needed lubrication, it woudln't make the noise he dscribes.

A very good idea. And something one with little experience can try first. He can put his hand on the panels and see if any is vibrating.
If not that, it's the contactor and I thind Dufas has some good ideas. Keep that up, Dufas, and you'll lose your right to your name.
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Squealing, not buzzing.
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On 7/18/2010 2:03 PM, AngryOldWhiteGuy wrote:

The buzzing is caused by a bit of rust or believe or not an insect caught in the armature of the contactor. When the contactor pulls in, it will buzz if the flat surfaces of the electromagnet is in any way interfered with. Sometimes a simple whack with a screwdriver handle will clear the debris and the buzzing will go away. Cleaning the contactor with contact cleaner or heaven forbid, WD-40 will often flush out the bugs, dirt and rust.
TDD
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On Sun, 18 Jul 2010 22:24:37 -0500, The Daring Dufas wrote:

<nods>
Heard this sound many, many times. Doesn't take much rust on the laminated core of the contactor or the plunger to make them hum.
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Thanks for all of the great information guys!
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