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Old 05-21-2013, 08:05 PM   #1
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Whistling Noise From Central Air Conditioner


Hello,

Today was a warm and humid day so I decided to fire up the Central AC and I noticed that after about a minute this very annoying whistling noise begins. I asked around and was told that it could be not enough air flow/leaky vent. I mentioned how could that be seeing as the furnace ran all winter without the whistle? (I should also mention this is in a house I recently bought so itís all new to me). He mentioned that the blower runs faster in AC mode which would make sense as to the difference. I have however opened up all the vents and even temporarily removed the entire air filter and the whistle remained. I donít think it has anything to do with the blower or the air pressure/vents since I noticed something else. When I manually switch the AC off the blower still blows for about a minute at the same exact speed but the whistle instantly goes away. The same goes for when I turn the AC on. No whistle for about a minute while the blower is going its normal speed but when the AC seems to ďengageĒ is when the whistle occurs. Iím thinking it has something to do with the refrigerant or a valve. Any suggestions/insights? Thanks!

-Bill

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Old 05-21-2013, 09:19 PM   #2
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Whistling Noise From Central Air Conditioner


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Originally Posted by knight508 View Post
Hello,

Today was a warm and humid day so I decided to fire up the Central AC and I noticed that after about a minute this very annoying whistling noise begins. I asked around and was told that it could be not enough air flow/leaky vent. I mentioned how could that be seeing as the furnace ran all winter without the whistle? (I should also mention this is in a house I recently bought so itís all new to me). He mentioned that the blower runs faster in AC mode which would make sense as to the difference. I have however opened up all the vents and even temporarily removed the entire air filter and the whistle remained. I donít think it has anything to do with the blower or the air pressure/vents since I noticed something else. When I manually switch the AC off the blower still blows for about a minute at the same exact speed but the whistle instantly goes away. The same goes for when I turn the AC on. No whistle for about a minute while the blower is going its normal speed but when the AC seems to ďengageĒ is when the whistle occurs. Iím thinking it has something to do with the refrigerant or a valve. Any suggestions/insights? Thanks!

-Bill
Could be freon whistling through the metering device. I've had homeowners tell me they notice it when the unit gets low on freon. May want to have freon levels checked. If not it could be some kind of a partial restriction at the metering device.

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Old 05-21-2013, 11:17 PM   #3
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Whistling Noise From Central Air Conditioner


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Could be freon whistling through the metering device. I've had homeowners tell me they notice it when the unit gets low on freon. May want to have freon levels checked. If not it could be some kind of a partial restriction at the metering device.
Thanks for the reply. As I mentioned I bought the house recently and decided to tidy up the condenser side a few weeks ago and decided to replace the insulation since it was worn. I found this:
http://imageshack.us/photo/my-images/19/1001148to.jpg/
Would that have any effect as well as the possibility of it being low on refrigerant? Thanks.
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Old 05-22-2013, 10:33 AM   #4
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Whistling Noise From Central Air Conditioner


It may make the noise in cooling only because the blower is at a higher speed for cooling. Try shutting the a/c off and running only the fan. Have you replaced your filter lately?
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Old 05-22-2013, 01:53 PM   #5
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It may make the noise in cooling only because the blower is at a higher speed for cooling. Try shutting the a/c off and running only the fan. Have you replaced your filter lately?
I temporarily removed the filter and the noise remained. Also, when the the t-stat is set to off and fan manually on there's no noise.
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Old 05-22-2013, 08:09 PM   #6
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Whistling Noise From Central Air Conditioner


refrigerant moving thru the system.especially with the cooling OFF but the fan in on.run the cooling at 65F to keep it on and block the top of the condenser outside so the air doesn't discharge into our face ...garbage can top with a coule of bricks.WHY this...trick blocking the air discharging will bring the head pressure up along with the suction pressure go down to the furnace and see if the noise is happening...not swetyou won't blow the compressor up just for 5 minutes... also put a screw driver to the insulated line/suction and thin raw copper line/liquid then your ear to it...do you hear anything.
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Old 05-23-2013, 09:10 AM   #7
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refrigerant moving thru the system.especially with the cooling OFF but the fan in on.run the cooling at 65F to keep it on and block the top of the condenser outside so the air doesn't discharge into our face ...garbage can top with a coule of bricks.WHY this...trick blocking the air discharging will bring the head pressure up along with the suction pressure go down to the furnace and see if the noise is happening...not swetyou won't blow the compressor up just for 5 minutes... also put a screw driver to the insulated line/suction and thin raw copper line/liquid then your ear to it...do you hear anything.
Hi Biggles,

Well, I did exactly as you said and the noise went down quite a bit. Down enough to not hear it from the usual living spaces. Also, I noticed when I put my ear up to the cold line outside the whistling noise is very noticeable regardless of the condenser being blocked. The hotline really didnít sound like anything. So, what does this mean? Thanks!

-Bill
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Old 05-23-2013, 09:50 AM   #8
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Whistling Noise From Central Air Conditioner


It means low charge.
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Old 05-23-2013, 04:11 PM   #9
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It means low charge.
Which means a leak no? Unless it was charged that way initially. The furnace is new and where the location of the evaporator and line set going into the duct I think they could have installed it without even touching any part of the AC. Guess I'll get a tech to charge it up?

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