Saturday, 29 December 2018

Fitting a dashcam to a Discovery 4

Another car another dashcam.

In previous cars I have always managed to find a suitable wire near to where I needed it to splice in to. The Discovery 4 circuit diagrams are so complex that it is difficult to identify a wire that will come on and off with the ignition and have sufficient spare capacity to use for anything.

I decided it was safest to run a wire back to the passenger fuse box and jumper off there.


I opted for Fuse 20, which is designated for a heated steering wheel, which I don't have. It's a 10Amp circuit, so plenty for what I needed.

Getting to the fuse box is easy, just depress the curved stays on either side of the lower glove box and it then folds down freely to gain a nice wide opening behind the dash.

Removing the interior A pillar trim is also amazingly easy. It has an air bag inside, so I was very careful. I fist disabled the airbag using the key turn on the end of the dash.

Behind the plastic airbag warning symbol, there is a single torx head screw. With that removed the trim pulls out easily.


The more scary, is removing the interior light cluster. It's held in entirely by clips. Grab the edge nearest the windscreen and pull. It takes some pressure to get it out but the clips will give with some care.

The end furthest from the screen has deeper hooks overlapping the headlining, so no point in trying to pull that end.


Threading a wire was not too difficult. I started from the fuse box end. The only tricky bit was getting it over the headlining. It was just luck that the wire went in the right direction and I could manage to reach it through the hole in the middle.


I took the opportunity to run an earth lead back to the dash because there is so much plastic that I could not find a good earth near the fuse box.


I found a handy M6 nut in the roof so I scratched and sanded down to bare metal to make a good earth.


I removed the end panel of the dash. It gave an improved view but was unnecessary to thread the cables. The panel is only held on by clips and just needs a good tug from the bottom edge to remove.


The metal spring clips sprung off and needed to be recovered.


I used a fuse piggy back jumper for the live and I powered the camera with a 12V to USB adaptor.


I ran the USB cable inside the mirror trim.


I filed a small notch in the trim to thread the cable.


Once connected I tested the camera before refitting anything.

Attaching the A pillar trim is fairly easy. It just needed the felt door trim pulled gently over the top and the screw refitted.

The interior lamp pushed back in easily. One wire did try to get in the way but just needed to be held in while pushing it together.

It's neatly installed and works nicely.

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Passenger Compartment Fuse Reference:
Fuse number, ignition or permanent feed and usage
16 Ignition - Cooler
20 Ignition - Heated steering
28 Permanent - Unknown usage
29 Permanent - Unknown usage
34 Permanent - Electric fuel cap
55 Ignition - Auxiliary sockets
63 Auxiliary sockets but the fuse is too tight to jumper off of.

There are plenty of unused fuse holders that have permanent live feeds but without knowing if they are connected to anything, it is a risk using a fuse jumper in them. It would be possible to use a single blade however the maximum current capacity is also unknown.

I prefer to use a known fuse for a system not fitted to my car.

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