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Thread: Rattling Noise After Cold Start With A/C On

  1. #21
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    If it helps, I had this happen on my last new car till the compressor broke in.

    The moving scroll inside the compressor needs to wear into the stationary scroll over-time. These compressors use a scroll that moves in small eccentric circles around a stationary scroll. There is a small amount of "slip" that occurs and when new, may cause a slight sound until oil, or refrigerant, starts to pass through the scroll.

    They are extremely durable, and more efficient than traditional piston-type compressors found in your older home HVAC systems (newer HVACS use scrolls now too).

    They are generally speaking capable of being entirely oil-free, though they do add oil to them in many cases to quell sounds, and further increase durability.

    Also, if the refrigerant has any lubricity properties to it at all, of which some refrigerants do, then the refrigerant will act as it's own oil in the scroll and an explicit oil will be completely left out.

    If anyone is wondering, I use to work in commercial refrigeration before I went back and became a software guy.


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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 51.7 mpg (US) ... 22.0 km/L ... 4.6 L/100 km ... 62.0 mpg (Imp)


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    Thanks for this post, as I'm sure some here may not understand how scroll compressors work. I read up on their operation when deciding on installing a geothermal system in our home.

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Wanted to bump this again. My compressor still makes this noise after what must have been hundreds or engagement events. Is this normal and common? Has anyone else taken their car to a dealer for this?

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    Quote Originally Posted by ahausheer View Post
    Wanted to bump this again. My compressor still makes this noise after what must have been hundreds or engagement events. Is this normal and common? Has anyone else taken their car to a dealer for this?
    It does appear as though this is normal. It took my mirage a little over an entire summer for it to stop making the noise. Since I live in texas, it got a LOT of use. I can't speak as to if anyone has taken theirs in for a dealer to look at it.
    Certified holder of useless car knowledge.

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    Quote Originally Posted by ahausheer View Post
    Wanted to bump this again. My compressor still makes this noise after what must have been hundreds or engagement events. Is this normal and common? Has anyone else taken their car to a dealer for this?
    It's possible it may not be worn in.

    But it's also possible that the scroll "slips" too much against the stationary scroll. If that's the case, you'd eventually need a whole new compressor as it will develop internal compression loss and loose it's "cooling power". To make it clear, you won't be loosing refrigerant, just the ability to compress it.

    It's not uncommon though, if it is colder outside especially, for it to make noise even if it is broken in.

    The part that makes me worry about using the "Defrost Button" in extreme cold is just that: it's really cold, and the defrost button uses the compressor to remove water vapor from the air. The issue is, that you generally can't run a compressor at temperatures under 50 F for a home unit, or 32 F (freezing) for a vehicle unit. That's a recipe for disaster over time, as the refrigerant will hydro-lock inside the compressor, and cause serious wear, and some serious rattling sounds too.

    I'm not sure if our cars are "smart" enough not to do that: run the compressor when it could damage it. But I also don't know too much about the refrigerant additives that could allow it to run in colder conditions for this vehicle, as there are some things they can add to R-134 to allow it run in extreme low temperatures.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 51.7 mpg (US) ... 22.0 km/L ... 4.6 L/100 km ... 62.0 mpg (Imp)


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  10. #26
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    A/C Rattle

    Quote Originally Posted by ahausheer View Post
    Wanted to bump this again. My compressor still makes this noise after what must have been hundreds or engagement events. Is this normal and common? Has anyone else taken their car to a dealer for this?
    My 2015 Mirage has 10,000 miles on it and is 1 year old and still does it everytime I turn the A/C on and it starts. Mine is an ES CVT. My co-worker also has a 2015 Mirage ES CVT with 14,000 miles on it and it is over a year and a half old and still does it. My dealer told me it is normal for this compressor and he checked 2 on the lot that were new and they actually did it worse than mine. So I guess it is normal, have you found anything else out by chance???

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    The A/C compressor is a scroll type compressor. By their design nature they're noisy at startup when the A/C engages. They are pretty refrigerant level sensitive though. If you have a really noisy one one have the charge level checked, it might be low. Members that have had their refrigerant recharged have reported much quieter operation and less cycling. Also, there have been a few A/C compressor failures long term, most likely due to low charge. The refrigerant provides lubrication to the compressor.

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)


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  13. #28
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    Quote Originally Posted by inuvik View Post
    The A/C compressor is a scroll type compressor. By their design nature they're noisy at startup when the A/C engages. They are pretty refrigerant level sensitive though. If you have a really noisy one one have the charge level checked, it might be low. Members that have had their refrigerant recharged have reported much quieter operation and less cycling. Also, there have been a few A/C compressor failures long term, most likely due to low charge. The refrigerant provides lubrication to the compressor.
    It does like a rattle noise for 2 seconds just when ai first turn the a/c on and after that it dont do it the whole time it is running. I know the fans in the Mirage run alot when the a/c is on. Do you think what mine is doing sounds normal? Or would you have them check it next time I go in for an oil change?

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    Quote Originally Posted by Mirage ES Navi View Post
    It does like a rattle noise for 2 seconds just when ai first turn the a/c on and after that it dont do it the whole time it is running. I know the fans in the Mirage run alot when the a/c is on. Do you think what mine is doing sounds normal? Or would you have them check it next time I go in for an oil change?
    Sounds like it's pretty typical but it wouldn't hurt to have the charge checked. If you have a shop that will check the charge level it might be cheaper than have the dealer checking it. It's not like it uses an exotic refrigerant or anything like that. Mitsubishi only covers the refrigerant level to 12k miles anyway, after that you're on your own.


        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)


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