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C5 A6/S6 (1998 - 2004)
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WRITEUP: $25 Tip on demand mod for pre-02 cars (should work on ALL tip cars - a6, a8, s4 etc.)
Posted by: halik (3959) on 2009-05-08 16:11:38

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Hey kids,
I just got finished with this little mod - it allows you to flip your car into tip mode using the steering wheel buttons/paddles. The only caviat is that the first click is ignored by the tcu, so to downshift/upshift from D mode, you need to double click the button. Also doing this mod will not alter the behavior of the shifter tip mode in any way.

Parts needed:
- Tiptronic steering wheel with ground wired to the regular ground (your tip buttons should light up with headlights, not just when you put the shifter in tip mode)
- ELK 960 relay timer ( manufacturers website here
- some wires and wire splicers from radioshack

Background info:
The way tip buttons work is that they have 12v across them that drops to 0 when you press them. Also I believe the ground lead for both of the buttons is switched open/closed by the TCU, depending whether it's in the tip mode or not. So the practical outcome of this is that the buttons won't light up when the headlights are on if the car is in D (since the tcu won't close the ground unless it's in tip mode). You need to rewire the steering wheel tip button ground to regular ground (brown wire on the shifter harness or anywhere else).

Now the pre-02 TCUs happily ignore the buttons unless the tip line is closed to ground(even when the buttons are energized), so that's where the ELK delay timer comes in. The basic idea is that when you click a steering wheel button (12v on it goes to 0v), it will close the relay and put the car in tip mode for some period of time. Once the time expires, relay opens and car goes back into D.


Installation:

First step for people with OEM tip wheel is to rewire the tip buttons ground to regular ground (brown), so that the buttons are energized at all time. To check it you should be able to measure 12V across the buttons or the simpler way is to see if the buttons light up with headlights with the car is in Drive. FIY Ground is the second pin on the airbag side of the clock spring connector, so just follow that down.

Next step is to wire in positive and ground wires to power the ELK timer. On the A6 you can tap into the connector labeled 30A right by the relay board behind the driver's knee panel thingy (green wire on in the picture). You can also find ground to the left of if near the dead pedal.
Run the two cables to the center console or wherever you want to install the ELK timer. Btw the timer draws 20mA off, so it shouldn't kill your battery.


Tapping into ignition +


Running the wires:



Set the jumpers on the ELK timer as follow (here's the manual
JP1 SEC
JP2 1-SHOT
JP3 BEGIN
JP4 A
JP5 +

ELK Wiring:
+ positive/igntion coming from driver's side
- ground coming from driver's side
TGR - tap into purple and blue wire on the shifter harness (down shift button/switch)
N/O - tap into brown (ground) button on the shifter harness
COM - cut the purple/green wire (tip mode switch) on the shifter harness in half and connect the half coming FROM TCU to this connector
N/C - connect the purple/green wire half going TO THE SHIFTER to this connector




Now start the car up, put it in Drive with the brakes on see if click the - button on the steering wheel puts the car into tip mode ( you should hear a click and the LED on the timer lights up). Once this works, you can play around with the pot on the ELK to set the time delay. If it's all good, you can mount the timer wherever you'd like, I'm including pics from A6. I should have a video in the next couple days.

*** Currently the tip switch only works with downshift button, I need to get some 12v diodes to make it work with both upshift and downshift buttons. Will update as soon as I test it out.


A6 mounting:
I shoved the thing behind the center console ash tray. The only thing you need to do is bust off the connector holders on the underside of the ash tray and relocate the cig light harness to the back of the ash tray.





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