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Dangerous side-effect of auto-disable of jack mode above 5mph

Discussion in 'Model S' started by HankLloydRight, Jul 16, 2014.

  1. HankLloydRight

    HankLloydRight Fluxing

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    #1 HankLloydRight, Jul 16, 2014
    Last edited: Aug 1, 2014
    NOTE: Update in post #14 .

    This is now the second time this has happened. I took my car in to get the wheels/tires re-balanced (different story). Anyway, the shop (Town Fair Tire) had a standard twin-arm lift, which they choose not to use, and instead, used individual floor jacks with a rubber jack pad -- one jack on each corner jacking point. Prior to jacking the car up, I put the air-suspension in "Very High" mode and turned on "Jack Mode". They jacked the car up with the floor jacks. While the car was jacked up, they slid the twin-arm lift arms under the car (they were unused, just in the way).

    When they went to remove the front wheels, the put in a brake-pedal bar to lock the front wheel brakes. This turned the car on. This is where the problem started. I have no idea why Tesla Motors has this "feature" but doing this AUTOMATICALLY disables JACK MODE, and the auto-leveling was re-enabled. But since the wheels were off the car, nobody noticed. Well, that's not true, since I had seen this happen once before, I immediately jumped in the pax side and re-enabled "JACK MODE". But what I did not realize in that short period of time, the suspension lowered itself to the "normal" setting with the wheels still off the car.

    We didn't notice the lowered position until they remounted all four wheels and lowered the car to the ground. Except this time, the car was NOT in the "Very high" setting, and the car is now resting on the twin-arm lift arms under the car (drivers side only) -- NOT on the jack points, but rather well into the battery area. Now there wasn't a lot of weight on the lift arms, as we could just lift the car with our hands and swing the arms to move freely, but not enough to clear the side skirts. So I had to jump in the driver's seat, and reset the air-suspension to "Very High", which it didn't really do at first -- it took 2 or 3 tries to get it to sync up and lift the car back up. Once that happened, the lift-arms easily swung out of the way.

    Once out of the way, I looked underneath for any damage to the battery cover and saw nothing at all (luckily). Now yes, should the shop not have swung the lift arms under the car -- sure. But what's most upsetting is that under these circumstances, the car AUTOMATICALLY disables JACK MODE and re-enabled the auto-leveling. This is a serious flaw, as I think at best, JACK MODE needs to be MANUALLY enabled AND DISABLED. At worst, the car should put up an error message indicating JACK MODE (which it already does). So why turn it off without an explicit action from the driver? Luckily this time there seems to be no damage to the traction pack or housing, but jeeze, if those lift arms were 1 or 2 inches higher, or there was some other obstruction under the car that does not clear on the normal height setting could lead to massive damage to the battery.
     
  2. ACDriveMotor

    ACDriveMotor Member

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    Is it because the car thought someone was trying to drive due to brake press and possibly weight on the driver seat? I imagine this is not a problem in an SC where they put the car into some service mode which disables automatic "safety features" that prevent driving in jack mode.
     
  3. HankLloydRight

    HankLloydRight Fluxing

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    Nobody in the driver's seat. And even if someone was trying to drive in Jack Mode, so what? Just throw up an error message. All Jack Mode does is disable auto-leveling. You can certainly drive in Jack Mode. The problem is that it disabled ITSELF without any warning or prompt. Huge fault/flaw in my opinion.
     
  4. stopcrazypp

    stopcrazypp Well-Known Member

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    If you haven't already, you should report this to Tesla. It could be a case that was missed in designing the system and can probably be addressed in future updates.
     
  5. yobigd20

    yobigd20 Well-Known Member

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    why would you need to use a brake-pedal bar to lock the front wheel brakes? the car is in jack mode which I would assume already locks the brakes...
     
  6. ACDriveMotor

    ACDriveMotor Member

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    I am not defending the behavior, simply offering an idea of why it might behave as it does/did.
     
  7. HankLloydRight

    HankLloydRight Fluxing

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    It's a tire shop and that's their standard operating procedure for any car. I have never seen any indication that Jack Mode locks the brakes on the front wheels, and even you would just assume that it does. Even the MS e-brake only operates on the rear wheels with independent calipers.

    Either way, using a lock bar or not, Jack Mode should never auto disengage.
     
  8. JPP

    JPP Active Member

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    AFAIK, brake pedal bar is to keep steering wheel in fixed centered position. Nothing to do with the brakes per se.
     
  9. HankLloydRight

    HankLloydRight Fluxing

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    I sent a long note to Ownership... we'll see if they respond.
     
  10. tezco

    tezco Sig P85

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    They may do this to make it easier to remount the tires (it's easier to line up the studs with the holes in the wheels when the axle is locked). They probably also torque the lug nuts while the car is on the lift, which also requires a stationary axle.
     
  11. BlkCld

    BlkCld Member

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    Sounds like they should have loosened the front wheel lug nuts before lifting just like any other car. Using the brake seems like the lazymans way that idnt want to bother bending down.
    Just tried mine. Jack mode on. Closed door. Powered down. Opened door stepped on brake. Powered up jack mode was still on. Sat in seat and pressed brake jack mode still stayed on until manually selecting off. Sounds like yours may have had a glitch.
     
  12. Zextraterrestrial

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    That is what I was thinking. It stays on until I actually drive over 5 mph or so... have changed/rotated wheels on the s dozens of times
     
  13. HankLloydRight

    HankLloydRight Fluxing

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    The only difference I can discern (since the same thing happened to me twice) is that they car was in the highest lift setting and in jack mode, then put on the lift. They would then put in a breaker bar to hold the brake pedal down (without sitting in the seat). This turns the car "on". There has to be some combination of holding the brake pedal down for X seconds without a driver in the seat that automatically disabled Jack Mode. Or some other combination of inputs that caused it to happen twice, at the same tire shop.

    I sent a note to Ownership, and the local SC called me to bring it in for a checkup next week. I suspect it won't repeat the same behavior, but I'll let them try.
     
  14. HankLloydRight

    HankLloydRight Fluxing

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    The SC today and they read the logs.

    Apparently, "JACK MODE" auto-disabled at above 5MPH.

    They claim that the car hit 5MPH pulling into the tire shop garage, which I find hard to believe, since I was parked right outside, put it in JACK MODE, then DRIVE, and inched into the lift area. They say the first time, it was 4.9MPH and the second time 6MPH.

    But since I've been unable to replicate the problem, I'm going to have to assume that's what happened, but I'm sure I didn't go that fast moving 10 feet into the garage.

    Still, I think JACK MODE should be only disabled via a specific action of the driver, otherwise, display an error message. But don't auto-disable above 5MPH. All JACK MODE does is turn off auto-leveling. Why is it necessary to disable that over 5MPH?

    And the SC was awesome -- I was able to buy my camera for the front camera kit, and they washed the car. Of course, as soon as I leave, there's a torrential downpour. :rolleyes:
     
  15. BlkCld

    BlkCld Member

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    Glad you figured it out. Maybe don't select jack mode until in the lift position just prior to getting out.
    Hmm the downpour sounds just like my BlackCloud luck
     
  16. mgboyes

    mgboyes Member

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    Jack mode auto-disables at about 5mph.

    On two occasions I've been to have work on wheels/tires and I have enabled jack mode (and very high, and disabling walk away door lock, and the tilt sensor, and the alarm, etc etc!) before handing over the keys. Both times I've had to go into the service bay after they moved the car into position to re-enable jack mode since they exceeded 5mph bringing it in from where I parked it.
     

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