Electrical problem, Audi A4


Veteran Member
Jan 15, 2005
Audi A4 1.9TDi Avant Quattro 2001 silver
We have a audi A4 1.9TDi avant quattro 2001. The engine code is ATJ.

I'm about to install cruise control, and I'm about to run the powerwire up to the stack. I was a bit stupid and had forgot to disconnect the battery when I was looking
on the back of the fuse compartment, so I shored on of the thick wires running into the fusebox, to ground for a second. After this some of the fuses does not get power
(the heater fan is not running, the turning signal is not working and a few others (all is connected to the same wire). But the car is running.

I have found that this wire (that I shorted to ground) is protected by a 80 AMP fuse in the box located in the engine compartment (the box where the "engine computer" and glow
plug fuse is). But this fuse has not "tripped" (looks OK and is ok when measured by a ohm meter). But I can't trace the wire running into this fuse (from the engine compartment).
Its a black wire running to this 80 A fuse (and a yellow and black running from the fuse to the fuse box inside the car), so does anyone knows where this fuse
gets the power from ?

And now to the weird part. Before this "accident" the wire running into the fuse box (from the 80 A fuse) had +12V on it (or the battery voltage), but AFTER the accident,
there is no voltage when measured from the fuse and to ground (or - on the battery), BUT, when I measure voltage between this fuse (80 A or on of the fuses inside the car
that gets their power from the 80 A fuse) and battery +, there is battery voltage ??!? So, in some strange way, the fuse now acts like a ground, and when I measure
between the 80 A fuse and ground, there is nothing (actually there is a short between this fuse and ground), but between the fuse and battery positive (+) there is
approx 12.5 volt.

Help is highly appreciated.

Tarjei Lundarvollen, norway