Analogue to Digital TV in 2002 S8

[HPsauce]

Had a quick look in my Bentley manual, first challenge was terminology, eventually found the "back-up light".
Pretty simple circuit, via the F125 switch through a few connectors (around the front "somewhere") into the loom and pretty much straight to the reversing light bulbs then grounded in the boot lid.
The wires seem to be blue/red all the way from the F125 if I can find them anywhere inside the cabin!

[IT]

Originally Posted by HPsauce

Fuses came to mind, but sadly the drivers footwell fuse (ideal location) for the reversing lights is shared with the automatic gearbox.

You have an S8, which means you have factory RNS-D.

The RNS-D has a reverse wire feed so that when you are going backwards, it knows to count the gala/abs wheel pulses backwards, otherwise the navigation would be hopelessly wrong if you reversed somewhere with poor GPS reception.

Pin 17 of the 26 pin connector on the back of the RNS-D, Should be blue with a red stripe. I strongly suspect it will be labelled as such on the top of the RNS-D.

[HPsauce]

Originally Posted by IT

Pin 17 of the 26 pin connector on the back of the RNS-D, Should be blue with a red stripe. I strongly suspect it will be labelled as such on the top of the RNS-D.

Many thanks Ian, I knew someone like you would have the answer off pat.

That pin is labelled RFLS which I now know stands for Rückfahrlichtschalter (reversing light switch). I was pretty sure there was such a connection but a look at the RNS-D and online didn't show anything definite.

The blue/red wire is very evident in the loom to that connector block. I'll attack that another day.

Meanwhile over lunch today I stripped out the trim above the battery, found the cables to the boot lid and tapped into the blue/red wire there for "future use" (probably a bit of testing before the final wireless install). I did test it to confirm it was the correct one.

A bonus of removing the trim was that I got good access to the collapsing grommet on that side and glued it back together. And sorted out some other bits that were a bit "irregular".
A downside was that the cable loom was wrapped in the most disgusting gooey certoflex mess I've ever encountered. White spirit sorted that out.

[IT]

Originally Posted by HPsauce

A downside was that the cable loom was wrapped in the most disgusting gooey certoflex mess I've ever encountered.

Yes, it is a bit grim..... I'm still haunted from when I had to strip out an entire loom to get all the bits for the electric rear seat install. My fingers were a sticky black mess for days. Had no trouble picking stuff up though....

[HPsauce]

Originally Posted by HPsauce

The blue/red wire is very evident in the loom to that connector block. I'll attack that another day.

Can't be bothered to wait, worked out that this was the final bit of wiring to go behind the RNS so "set to" this afternoon.

All done, wired in new power source(s) for DVB-T and reversing camera input/relay and it's working fine (only camera at present); thanks Ian.

Just need to get the RNS fully back into place; that will need some very careful positioning of the cables as it slides in.

Then there's loads more work in the footwell to rig up the DVB-T tuner, fit the tuner/camera changeover relay (in the post!) and so on.

[Architex_mA8tey]

I would still put the aerial wire at the top of the rear window and "hide it" by keeping it tight to the rubber at the top so that you cant see it in your reversing mirror view - I think that would be better than either a side window or the front where you would see it all the time

[HPsauce]

I'll test them all and see what works, though the side window is visually much the worst.

The way the roof lining fits and overlaps the glass means that the windscreen may work well and still be completely hidden.
The rear window could potentially be the same but there's the complication of the heated rear window and embedded aerials.

[HPsauce]

Originally Posted by HPsauce

Fuses came to mind, but sadly the drivers footwell fuse (ideal location) for the reversing lights is shared with the automatic gearbox.

Thinking this through, that fuse (3.6) is "probably" just for the reversing light circuit, it's connection to the gearbox being that the circuit goes through the (totally mechanical) F125 switch.
Though the connection to the RNS is much more convenient for access anyway.

It does also mention cruise control (FL so not a separate ECU ) in the drivers manual and is connected to the RNS and parking sensors in some way, presumably in all those cases for "information" purposes not power.

Given it's a 10A fuse and I now have a pair of relatively low-power LEDs in place of the original 2 * 21W reversing bulbs my little electronic additions are not going to cause a problem.
(No idea what the power consumption of the LED bulbs is, they came from AliExpress and were advertised as 50W which is clearly nonsense. Presumably that's the equivalent filament bulb so I'd guess about 5W each)

[IT]

Its worth noting that on cars with factory TV the rear screen is supplied single pane to allow the TV signal to get through the glass.....

The only audi I'm aware of that has TV aerials around the windscreen would be the TT roadster, for obvious reasons. The A4/5 cabriolets have them in a very thin section of the boot lid from memory. TV reception is quite fiddly, hence why the factory setup has 4 separate aerials and then a diversity switcher to pick the strongest one.

Presumably as you have an V8, and no TV, your rear screen is twin pane like the rest, which will hamper signals somewhat.

I'm definitely with Neil, I can't think of anything more un-oem that seeing bits around the windscreen visible whilst driving.... Would defo have to be out of sight at the back somewhere for me....

[HPsauce]

Yes, I assumed the rear screen was twin-pane and the filaments for the heater etc. would further inhibit reception, hence looking at the front as well where there is a possibility of totally hiding the aerials.
As noted, I'll test all options and my new tuner has 2 (though not 4) diversity aerials/tuners.