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A/C compressor question

4748 Views 18 Replies 11 Participants Last post by  indyflick
As you can well imagine, living in Tucson, the A/C spends a lot of time running. In fact, my battery guess-o-meter said 32 miles this morning, primarily due to the heat.

My question is more curiosity than need-to-know, but I've listened to the compressor many, many times and it sounds like it is a variable speed unit. I did some searching on this forum and learned that the compressor is A/C (alternating current), 3-phase, and 300 volts. But, I did not find an answer as to whether it is multi speed or variable speed.

My home A/C compressor is multi speed, so I'm familiar with that as the two different speeds are very distinctive. The Volt, however, certainly sounds like a variable speed unit. Just curious if anyone knows for sure.

I was certainly pleased to read in my searching that the A/C compressor is considered part of the Voltec system and is covered under the powertrain warranty. Another big plus for the Volt, and for GM.
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I agree it's a variable speed compressor. Similar area as the OP, central CA and with the recent heat wave I can definitely hear the compressor making sounds from everything between the quietness of a refrigerator to what sounds like a jet engine from a couple hundred feet away. Certainly not a 2 or 3 speed difference.
Have you experienced less performance than usual when running the A/C? It's possible it's running at higher speeds initially to achieve an ideal pressure differential. If the refrigerant level is low or the performance of the compressor is reduced (worn, bad reed valves, etc), it may be running harder to achieve the proper pressures more quickly. Once the ideal pressures have been reached, it just has to maintain them, which would explain why the speed ramps back down to a more normal and less noisy state after a short period of time. Remember, unlike a belt driven unit that relies on engine speed and a control valve to determine the stroke size, the Volt unit is completely self-contained and uses data provided by one of the computers as well as an electric motor not unlike your refrigerator compressor to operate the refrigerant pump. It might be worth a trip to the dealer to have it inspected, especially since the compressor itself is covered under the Voltec warranty.
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On the hottest of days, mine ramps up and usually stays there. But on more normal days, it's rare that I even hear more than a slight buzzing from the compressor. I know we had a series of 100+ days here in the central valley which had the compressor running very hard making it quite noticeable. However on days when it's about 80 or so I think I hear the fans more than the compressor and it never really seems to ramp up to it's highest speed and reduce as the OP has described. It looks like we will have some cooler weather this week and I can do a test with mine to compare and report back.
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