I know this forum isn't as active as some of the other models, but I wanted to start this topic and possibly one day fill in all the details for anyone crazy enough to attempt this like I did.
I have a 2007 S-Line 4.2 Q7, which I bought used (2015) with just about every available option besides Air Suspension and Adaptive Cruise. I didn't really care much at the time, but over the years I realized I wished it had the Air Suspension.
After tons of research, I decided to do the retrofit, but I had to do it my way. On the cheap. If I bought all the parts separately, I could have easily spent $3,000 on this mod. But overall I only spent $300.
The key to this whole deal is that the Q7, Touareg, and Cayenne all came with the same Air Suspension in the early models. Touareg had the same basic components as early as 2004. I noticed that the models with AS sold for relatively the same price as models without it, mainly due to the stigma of AS being overly complex and frequently broken. After doing this retrofit I completely DISAGREE, I believe the system is actually rather simple and only a handful of common issues arise.
I bought a used 2004 Touareg V8 with AS, and I de-converted it to regular steel springs from the Q7, swapped in the black "cup holder" where the AS switch is in the center console, and sold it at a $400 profit after I cleaned it up a bit. I would say about 25% of the early V8 Touaregs have AS, you can always tell from the control knob on the passenger side of the center console. If it doesn't have AS, there is a blank "cup holder" there. Look for a low mileage example with the AS working 100%. You can also use a Cayenne Turbo, as all Cayenne Turbo came with AS standard.
I harvested from the Touareg:
-Air struts
-2/4 level sensors (the other two I left for the adaptive Xenon lights) but if you are using a parts car you can use all 4 level sensors.
-The air lines, compressor, and tanks (2)
-All four ABS harnesses, since the strut valve wiring is part of the ABS harness. You could just wire those connectors separate, but I was trying to get as close to OEM as possible.
-Acceleration sensors (2 in front 1 rear)
-Fuses and Relays
Wiring: I tried to harvest the intact wiring harness from the Touareg, but that proved close to impossible. I got about halfway and decided to just buy a complete body wiring harness from an eBay dismantler. This ended up being the best path, since I bought a body wiring harness from a Cayenne Turbo (they all have AS) and didn't want to rely on the dismantler to tell me if the car had AS or not.
The Cayenne wiring harness was only $300 and turned out to be a closer match to the Q7 wiring than the Touareg.
The rest of the parts I bought used on Ebay:
-Q7 AS control module
-Trunk lowering switch and trim panel (try to find one with a pigtail attached for the switch. I ended up having to make my own male connector, and it's not an exact fit plug but it works).
-2 missing level sensors. If your Q7 has adaptive xenon headlights like mine did, the existing level sensors will not work.
The hardest part of the job was making my own wiring harness and running it all. I used the Q7 wiring diagrams, Touareg wiring diagrams, and Cayenne wiring diagrams to make sense of it all. About 75% of the wires were already in the correct pins on the module side. Just had to double check them all and remove some extra wires. I believe the Cayenne/Touareg harness has wires into the cluster connector for lights etc, and the Q7 does not. The Q7 connects to the central convenience module instead, which is right next to where the AS module goes behind the pass side trunk panel.
I ran the majority of the wiring harness under the car next to the air lines in the cavity below the running boards. The factory system runs both inside the cabin, under the carpet but I didn't feel like ripping my interior apart after taking most of the Touareg apart. Plus if there was a problem with the wiring/lines, I wouldn't be able to get to the, easily if they're under the carpet.
Once I hooked it all up, I had to recode a bunch of modules including the ABS, ECU, Central Convenience, Cluster, and enable the AS menu option in the hidden "Green Menu" in the MMI. Once I did that the system came to life, filled itself up and everything has been great ever since.
If anyone has any questions or is interested, I will try to gather the pictures I do have from the whole process and share any more details for future crazy people like myself.
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2011 Dieselgate Q7 TDI..... patiently waiting for my warranty to expire!!
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