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Anyone experienced AC vibrations?

Discussion in 'Model S' started by zer0cool, Aug 6, 2015.

  1. zer0cool

    zer0cool Member

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    So got a 70D just over a month old. I have experienced this high frequency but low amplitude AC vibration, maybe twice. Both times they just random came on in the afternoon, generally when I leave from work... (it's been 90+ this summer almost all summer) I didn't know what was going on the first time... just felt this really high frequency, but very low amplitude, like you can notice it, but not sure where it's coming from type of vibration... It seems to exist everywhere, on the steer wheel and the seat... it's not terrible but just slightly annoying. I couldn't tell if it was the road, tires, or what. I felt it for some time but then it spontaneously disappeared maybe a day or two later. I thought that it could very well have been mental, like anxiety or something like that... so didn't think about it further.

    Then it happened again yesterday, right after I started the car in company garage. I felt the vibration the whole way home... not worse than first time, and I decided to figure out what it was, so at a stop, I turned off audio, still vibration, so turned off AC, and all vibrations were gone. Then I immediately turned the AC on, and there were no further vibration, and no vibrations after I got going again, and it's been good today...

    Is this something others have experienced? I assume something the SC can fix? But the problem is they may not be able to reproduce the problem since it kind of comes on spontaneously... and is not persistent.

    Thanks
     
  2. Cyclone

    Cyclone Active Member

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    I've had this happen to me a couple times. It is related to the intense, stagnant heat that may be in/around the car. Basically, the compressor will often run on "high", but sometimes it goes to "max" and kicks into overgear. When that happens, I experience the same as you are describing. Turning the a/c off and then on usually causes the compressor to go back to "high" instead of "max". The reason why this doesn't happen all the time (as far as I can figure) is that the compressor provides support for the cabin and the battery. Thus, it requires both to be at extreme temps for that to go into overdrive.

    The easiest way I see to avoid this is to precool the car when walking out. After 5 min, its done enough to ramp down on its own, or the car is cool enough that when you turn the a/c off and then back on, it needn't go to max again. I wish there was a better answer!
     
  3. zer0cool

    zer0cool Member

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    The problem is in both of my cases the issue appeared to be continuous until the AC was restarted. Both times, I detected the issue when I left work and felt the vibration all the way to home. However in the 2nd time, when I restarted the AC on the way home, the vibration sensation went away... so it's not something that just happens in the first 5 mins of the drive but appears to continue until restarted...
     
  4. JMG

    JMG Member

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    All I know is living here in Texas, the car will make some strange noises (and resulting vibrations that you can feel) in order to cool the battery pack and to power the HVAC. I don't believe its anything to be worried about, if its the same thing we're talking about.
     
  5. Cyclone

    Cyclone Active Member

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    In my car, it starts to ramp down after about 15 minutes. It doesn't get to normal until about 25-30 minutes into my drive. Thus, after 5-10 minutes, sometimes I turn the a/c off and then on to avoid the vibration for another 10-20 minutes.
     
  6. DoctorV8

    DoctorV8 Member

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    Agreed.
     
  7. Max*

    Max* Autopilot != Autonomous

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    Yep, SC said it's normal.

    It's very intense in the passenger wheel well, but I feel it on the steering wheel too.
     
  8. ZBB

    ZBB Emperor

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    Keep in mind that the AX compressor in the Tesla is variable speed. When it runs at full speed, it does get relatively loud and can cause vibrations. Used to be worse for those of us with earlier cars -- but Tesla redesigned the bracket that holds the compressor to the car and added an acoustic blanket in that area. I had that retrofitted a while back, and it has helped reduce the impact. But its still noticeable at full speed...
     
  9. SomeJoe7777

    SomeJoe7777 Marginally-Known Member

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    The vibrations don't come from just the A/C compressor. If it's hot enough outside and you need more than some threshhold of cooling for the cabin+battery, the radiator fans will come on as well. These are the source of most of the vibration, and they're the same fans you might hear when the car is supercharging.

    These fans draw a lot of power as well -- you can tell if they're on by looking at your kW meter. A/C compressor and cabin fan alone while the vehicle is stopped will only show around 1 kW, maybe slightly more. If the radiator fans are also on, you'll see closer to 4 kW.

    I theorize that the "range mode" setting (in addition to maximizing torque sleep) reduces the maximum cooling capability of the A/C such that the radiator fans are never necessary in order to make sure that power is saved.

    We're having 100° + heat here in Houston at the moment, if I turn the temperature on the A/C down to LO, radiator fans will come on within just a few minutes. Moving through stop-and-go traffic on the way home the past few weeks has been averaging close to 500 Wh/mile of power use.
     
  10. Cyclone

    Cyclone Active Member

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    Not to discount Joe as his description of the fans is indeed accurate. That said, in my case, that is not the source of the vibration I felt as I manually turned the fans to 1 and continued to experience the vibration I was incensed about. Now, overall, that reduced vibration, but the one that "scared" me didn't go away when turning down the fan speed. It also doesn't come on when I put the fan on 11 either.

    But again, Joe's description of the fan is accurate. On 11 they are loud and draw lots of power.
     
  11. scot

    scot Member

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    The AC works by having a blower in the car as well as fans under the "hood" area. The setting in the car only adjusts the internal blower motor.

    The fans in the front of the car work by pulling air across a unit called a condenser (looks like a radiator) which is heated by the compression of the refrigerant flowing through the system. When we say the system is "multi-speed" or "variable" it means the compressor can work at various rates, compressing more or less refrigerant as needed, and generating more or less heat. The most efficient way to do this is to cool at low levels for longer periods of time, which it does this by monitoring all of the various pressures and temperatures of the system and adjusting the compressor to suit.

    What you need to do is get push the limits of the system a bit, make sure the condenser has very little air flowing across it (car sitting still for a while is fine, don't block anything) and turn the temperature down to low, open up your windows and let'er rip for a while. It will start to get to max compression and heat generation after 10 minutes or so, which should force the fans to go into overdrive.

    You should, during this process, start to notice the vibration. If it comes up and you don't hear the fans (not blower) kicking in, it is probably the compressor. If you hear the fans, now you know.

    What you should check is to see if your condenser and radiators are blocked in any way. Leaves or whatever. If so, the car will need extra cooling because driving down the road is normally enough for the car to keep everything within spec.

    If it is the compressor or the fans and you think it is a problem, you should talk to service and tell them how you determined what was causing issues. Might help.
     
  12. SomeJoe7777

    SomeJoe7777 Marginally-Known Member

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    The cabin fan that you can control (from 1 to 11 on the touchscreen) is a separate fan. It circulates air throughout the cabin.

    The radiator fans (two of them, in the front of the car behind and below the headlights) you cannot control. The car will activate those to cool the refrigerant if required. These are the ones that vibrate and draw a lot of power.

    Remember that in the A/C system there are two evaporators for cooling. One is for the cabin, the other is to cool the system coolant flowing through the battery, chargers, motors, and inverters. Depending on how you're driving, whether you've recently charged, etc., the car may need to remove heat from the system coolant as well as the cabin, which could result in the radiator fans coming on even if the cabin isn't demanding high cooling.
     
  13. Cyclone

    Cyclone Active Member

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    Thank you Joe. I indeed was thinking of the cabin fan. Scot's explanation above coupled with your additional information for around two evaporators clarifies things significantly.
     
  14. cassiri

    cassiri Member

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    Mine makes quite a bit of vibration and noise that occurs fairly frequently. Where I am in SoCal it is rarely above 79 degrees so I don't see how my system is being heavily taxed. The noise comes on in stages, ramping up to a peak frequency and then dropping off in stages (maybe 5 in all) Each step is louder and sounds like a compressor motor spinning faster and slightly out of balance. I had it looked at once and was told nothing was wrong. I get that the noise will be more noticeable with no ICE to drown it out, but this is really annoyingly loud. As someone said before,cycling the compressor off/on resets it and restores peace and quiet if briefly.
     
  15. Khatsalano

    Khatsalano Member

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    Yes, the AC is not a silent stealth thingy. I've heard all kinds of weird noises, including what you've described. It only happens when the AC is working hard though.

    - K
     
  16. dusterbuster

    dusterbuster Member

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    I felt/heard a similar sounding vibration last weekend on my 2012 CPO car. Seemed quite loud/harsh and I was a bit surprised, and could feel the vibration through the brake pedal. Vibration/sound disappeared when I turned off the AC. I turned down the AC from Max and the sound/vibration went away. It was 90+ degrees in LA, so car was hot. Glad to hear this is semi-normal behavior, although might ask about the acoustical blanket/bracket upgrade the next time I go in for service.
     

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