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A/C compressor question

4738 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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My A/C compressor has developed a new habit over the last couple of weeks. When I first start my 2014 Volt now, if the A/C is on (any setting), the compressor runs at very very high rpm for 15 to 20 seconds and then immediately drops to an imperceptible RPM and stays there. It does this same thing even when I have climate set to Eco, fan speed 1, and temp just below ambient. The first time it did this I actually thought the Engine had started for some reason. I can feel the compressor running vibration through the steering wheel and I can also hear the compressor running. By the way, when its at that high RPM if I quickly turn the A/C off, the compressor will turn off - no time delay. Prior to this new behavior I never heard or felt the A/C compressor regardless of the climate settings. Anyone else experienced this?
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.
Thanks for your thoughts. The A/C performance doesn't seem to have changed however the weather has been cooler over the last few weeks. I will take your advice and contact my dealer.
My 2013 has always run a startup "cycle" where the pump comes on, goes through it's stages (you can hear it step up, up, up, and then down, down, down) and then either shuts off or runs at a low speed. I assumed this was normal since it always does it in warm weather.
Hmmm, that appears to be yet a different behavior. How long does the startup "cycle" take?
I thought I had an AC compressor issue. My Volt is at the dealership right now for what appears to be a transmission issue. But I asked them to also check the loud A/C compressor. I was hoping it could be replaced under the Voltec warranty. Turns out it wasn't an AC compressor problem but rather the issue is with the Heater Coolant Pump (part number 13597899). They tell me that pump is not covered under the Voltec warranty. About $700 for parts and labor. Solves that mystery. Hopefully they'll get the transmission fixed soon. That of course is covered under the Voltec warranty.
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