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  #13  
Old 06-12-2011, 11:21 AM
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Re: pulling a wheel off with QL

I could be wrong but it was my understanding that it didn't matter if the whole jeep was lifted off the ground. I thought the only time it may cause a problem was if one wheel or one side of the jeep was lifted. Also could someone post what the procedure is for disabling the system is and also for putting it back in service.
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  #14  
Old 06-12-2011, 11:27 AM
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Re: pulling a wheel off with QL

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Originally Posted by jp467 View Post
I could be wrong but it was my understanding that it didn't matter if the whole jeep was lifted off the ground. I thought the only time it may cause a problem was if one wheel or one side of the jeep was lifted. Also could someone post what the procedure is for disabling the system is and also for putting it back in service.
They don't differentiate between all 4 and one wheel but you're right, it's not a big deal when on a lift that takes all four off the ground at the same time though I have seen other systems try and level as the vehicle is being lifted because most lifts will raise one end a little more than another.

The procedure is simple, with the doors closed press the up and down buttons simultaneously until the EVIC displays that the system is locked (about 10 seconds). Do the same to unlock the system or simply drive it. It will unlock above 15 mph.
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Old 06-12-2011, 11:29 AM
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Re: pulling a wheel off with QL

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Originally Posted by Frank TJ View Post
I was wondering this myself. What I have come up with is this. The owners manual states to disable the QL when changing tires, etc. It also gives specific jacking points that are on the unibody, not any part of the axle/suspension.

What I see is that if you start jacking one corner up without disabling QL it will try to level the Jeep. I can't see how this in itself could cause the Jeep to fall off a jack because the jack is now acting like the missing tire. I personally think it has more to do with the QL getting out of whack and possibly one corner extending to ORII and the rest at normal???

I recently had the tires rotated at the local discount tire. The whole jeep was lifted and all 4 tires were off the ground. We disabled QL and I watched has the Jeep was lifted. The suspension extended to full extension just like any other conventional suspension. If we had not disabled the QL I'm thinking the airbags would continually be pressurized as the jeep was being lifted. This would result in the airbags being at a different setting than the computer thinks they are. Possibly over extension???

Not really sure on this topic. More research needed.
It's not nearly as complicated as you propose. The system will actually try to bleed air from the bladders as the vehicle goes up and since the sensors will not detect a drop in the vehicle the compressor will continue to run until it overheats. This assumes it tries to level, which it shouldn't if the ignition is off and/or a door is open. Locking the system just makes sure it doesn't try.

On thing I've noticed is that when the truck is lifted nitrogen seems to get pulled back into the bladders so when you set it back down it's at roughly ORII height. It does the same whether it's locked or unlocked so obviously there's something going on that's not intuitive. Regardless, it levels out just fine once you unlock it.

As for falling off the jack, it's exactly as you describe, as the system tries to level and it can't lower the side with the jack it will raise the others. Falling off the jack is a worst case event but if you've ever tried to set a car on 4 jack stands one corner at a time you will understand how raising one end can push another end in directions you don't want it to go.
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Old 06-12-2011, 11:33 AM
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Quote:
Originally Posted by mjw930 View Post
It's not nearly as complicated as you propose. The system will actually try to bleed air from the bladders as the vehicle goes up and since the sensors will not detect a drop in the vehicle the compressor will continue to run until it overheats. This assumes it tries to level, which it shouldn't if the ignition is off and/or a door is open. Locking the system just makes sure it doesn't try.

On thing I've noticed is that when the truck is lifted nitrogen seems to get pulled back into the bladders so when you set it back down it's at roughly ORII height. It does the same whether it's locked or unlocked so obviously there's something going on that's not intuitive. Regardless, it levels out just fine once you unlock it.
So it's more of a problem with screwing up the QL then a safety
issue.
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  #17  
Old 06-12-2011, 11:40 AM
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Re: pulling a wheel off with QL

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Originally Posted by Frank TJ View Post
So it's more of a problem with screwing up the QL then a safety
issue.
On a 4 wheel lift I would agree, on a 1 wheel lift (jack) it's more about safety that protecting the system.
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  #18  
Old 06-12-2011, 12:44 PM
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Re: pulling a wheel off with QL

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Originally Posted by ternst View Post
Why would you ever start your car when you have it jacked up? That seems like you are asking for trouble in many ways - what a dumb thing to do - but I guess there are lots of stupid people driving cars. There is no problem changing a tire on the Jeep if you have QL and don't disable it, and I don't really care to trust you, ha, ha....
A better question is why would you ever disregard the manual and do such maintenance without putting the car into jack-mode?

I don't have a QL GC, but I've had several cars with air suspension - all have had some kind of lock out while removing a tire. I have no doubt that you safely completed your work without the lock out, but WHY? Its not like its an in-depth or time consuming activity to engage this safety feature.
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Old 06-13-2011, 04:51 AM
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Re: pulling a wheel off with QL

He is probably trying for a spot in the Darwin awards....
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  #20  
Old 06-13-2011, 02:23 PM
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Re: pulling a wheel off with QL

As for starting the engine while jacked up, that happened to me accidentally while changing my wheels.

I did diable QL, had the right front jacked up and while changing the wheel I was surprised when the horn chirped twice and the engine started. THE KEY FOB WAS IN MY POCKET AND HAD SETOFF THE REMOTE START BY ACCIDENT. Luckily nothing happened, I turned it off remotely and left the FOB out of my pocket till I was finished.

Luckily QL was disabled as the manual suggested.
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