There is a module, called a LLAMS and made in Australia, which lets you control the ride height of the Discovery 3 and 4 air suspension.
http://www.llams.com.au/
I have just emailed the guy who makes them and he is interested in making a similar module for the Grand Cherokee Quadra Lift system.
He asked me if I had access to a circuit diagram of the wiring for the Quadra Lift system...
Does anyone have one or know where one can be found?
He is near Wagga and if there is someone who has Quadra Lift and is interested in letting him have a look at your car, please let me know. I would happily lend him mine, but I am in Melbourne...
Cheers
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