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A/C Compressor--is this normal?

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Old Feb 22, 2010 | 03:35 PM
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A/C Compressor--is this normal?

With the defrost on, the fan at '1', lowest, and stopped at a light or at idle, when the A/C cycles on, there's a 'puff' or kind-of a 'breath' the blower seems to take. Is this normal?

I can't hear it if the blower is on 2 or higher and when driving since the fan noise/road noise covers it up.

Thank you for any help/input!!
 
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Old Feb 22, 2010 | 03:47 PM
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It's problably the system's pressures equalizing when the compressor cycles off?
 
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Old Feb 22, 2010 | 04:56 PM
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Well, do you hear the noise in your truck? If its a normal thing, cool! If not, I would like to have it looked at ASAP before the warranty expires.
 
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Old Feb 22, 2010 | 09:22 PM
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I don't own one, I work on them.... If your def is on, your compressor will be cycling on/off. When it goes off, the 2 unequal pressures in your AC system will try to equalize thus causing a hissing sound through the orifice tube. Don't take my word for it though, take it to the dealer.
 
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Old Feb 22, 2010 | 09:26 PM
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It could also be your compressor lowering the idle thus taking more voltage from the system as it locks up(until the idle picks back up). This could cause a slight change in fan speed and could be interpretted as a breath like sound.
 
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Old Feb 22, 2010 | 11:11 PM
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Thank you for your input. I don't notice any change in the RPM--I did try to watch for that. I'm just surprised to see/hear this much with such a large motor. I came from a 2.4 liter inline 5 and with that one, the RPM changed when the A/C cycled, but there were no other noises, etc.

Where is the orafice tube located, anyhow? Is it close to the cab? I did stop at a dealer several weeks ago and asked about it. The service tech felt it was normal as well, and he owns one!!

Thanks again!

PS-- I LOVE my truck!!
 
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Old Feb 23, 2010 | 05:23 PM
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The orifice tube is inside the A/C high pressure line near where the line goes into the firewall/evaporator. You can't see it without disconnecting the line(you have to recover the refrigerant first and vacuum the system though to disconnect lines).
 
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Old Feb 23, 2010 | 05:27 PM
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Thank you again for the info and help!!
 
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