Hi!
I got A6 C5 with electronic front differential lock. As I'm involved in trophy-raid (I'm not driving in Tophy raid with A6 ), sometimes it happens to drive in muddy places, where some viewers cars have stuck, until now - i got throug (if You do not know, what trophy-raid is: Trophy raid in Latvia - http://video.google.com/videoplay?do...317&pr=goog-sl , in Russia - http://video.google.com/videoplay?do...04738377042391 ). Original electornic difflock seems to work like this: one wheel spins faster than other for few seconds, then difflock tries to engage (I hear some metalic rumbling), then difflock engages, grip gets significantly better. The problem is, that difflock stays engaged only for about one second. Then it releases.

I got an idea - electronic difflock has to have significant power supply, so I just add my own relay to this power supply line, the relay then would be connected to custom "engage" button. The questions are:
1) is it possible?
2) what will ECU think about this?
3) how long electronic difflock can be engaged (don't want to burn it)?

 

If you have the system i think your speaking of it doesnt work the way your thinking. The c5 98-04 a6's electronic diff lock has nothing to do with the differential. Its a function of the abs control unit. The vehicle is equiped with an open differential that sends power to the wheel with the least resistance. So if one wheels in the mud and the others on dry pavement the wheel in the mud gets all the power. This results in the muddy wheel spinning really fast and the wheel on the pavement going nowhere. The abs control module sees this and intervenes. It applys the brakes to the wheel in the mudd. This increases the resistance to the wheel in the mud. In turn the power is transfered to the wheel with least resistance, which is the wheel on the dry pavement.

So theres really no a way to engage this function as the decision as to apply the function is decided inside the control module. Theres no input to activate it.

There is also a safeguard build into it. If the control module sees that the brakes are getting too hot, it will disable the edl,electronic diff lock. There are no temp sensors as the temps are calculated thru time brakes are applyied and vehicle speeds. This may be why your edl seems to be malfunctioning. It may be turning itself off to prevent damage. Dont rule out a failed module or pump thou. Have the abs scanned for fault. Part of the system may be malfuctioning.