Totally powered down central air sounds like poor mans pipe organ


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Old 09-10-10, 04:09 PM
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Totally powered down central air sounds like poor mans pipe organ

We get a very strange sound coming from our central air conditioning outside unit when it is shut down at the end of the day. It sounds like gas is equalizing past a valve that is not quite shut or open. Similar to the sound you can get when you have a washer going bad on a water valve and you don't quite have the valve turned off. The system seems to be working fine. I am worried that is a indication of a problem about to happen. I went as far a top put the units breaker out so I was sure all electrical parts of the unit were shut down. Did not have any effect on the sound. The link below is to a wav file of the sound.

Any ideas what valve the gas may be leaking through?

http://www.thetatek.com/test/DSCF6818.wav
 
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Old 09-10-10, 05:07 PM
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Wow....I sure hope one of the pros can chime in! That sounds like some sort of foghorn or something. I have never heard an A/C unit make that kind of noise before.
 
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Old 09-10-10, 05:57 PM
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If this is a heat pump I would say it is the reversing valve
 
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Old 10-01-10, 10:16 AM
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I would say you have bad valves in your compressor. If the valves are bad, the system will still run but not as efficiently and the pressures will equalize between the high and low sides during the off cycle. You can check for bad valves by closing the King valve on the suction line (inlet of compressor). With gages attached the compressor should be able to pull the low side into approx. 20" of vacuum, discharge should be in the area of 100 psig. If these pressures can't be reached then the valves are bad. Semi-hermetic compressors may be able to be serviced and valves replaced, however, most residential units have fully hermetic compressors and the whole compressor will be replaced.
 
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Old 10-01-10, 12:03 PM
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Severe overcharge get it serviced soon.
 
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Old 10-01-10, 01:16 PM
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Exactly same sound I get from my propane tank that I use to BBQ in my backyard. I go through 6 or 7 tanks per year. this is the only one making this type of noise. I can shut it off and turn it back on a few times, and the noise went away, but next time it will do it again. I use the same valve for all tanks, so it is not the valve. but it got something to do with the valve, if I push the valve down a little or push to the side a little, the noise stops. (this won't help your A/C noise, but at least you know you are not the only one heard that strange noise.)
 
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Old 10-01-10, 01:44 PM
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Originally Posted by Former Member
Severe overcharge get it serviced soon.
Severe overcharge could be right, overcharge may result in liquid getting back to your compressor (a.k.a. liquid slugging) and it will destroy your compressor!
 
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Old 10-03-10, 07:01 AM
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Originally Posted by kyoung22
I would say you have bad valves in your compressor. If the valves are bad, the system will still run but not as efficiently and the pressures will equalize between the high and low sides during the off cycle. You can check for bad valves by closing the King valve on the suction line (inlet of compressor). With gages attached the compressor should be able to pull the low side into approx. 20" of vacuum, discharge should be in the area of 100 psig. If these pressures can't be reached then the valves are bad. Semi-hermetic compressors may be able to be serviced and valves replaced, however, most residential units have fully hermetic compressors and the whole compressor will be replaced.
Do not use the compressor to pump the system down!!! This is a sure way to kill a compressor! You can test valves and reversing valve if installed with your fingers. You disconnect the outdoor fan and allow the unit to stop on high pressure switch. Then feel the suction line at the rev vlv and at the compressor. If the line gets hot quiclky at the valve it's the valve, if hot quickly at the comp it's the comp valves.
 
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Old 10-04-10, 05:14 PM
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I was talking about doing the pump down on a split a/c system not a heat pump. That's how I was told to check for bad valves on a hermetic compressor in a a/c only system. Is the compressor still at risk if it's not a heat pump??
 
 

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