Wolo 847 Siberian Express Horn on Disco 2 - Part 2 - Overhead Control Panel and Electrical Wiring

Overhead Control Panel

In Discovery 2, the console above your head where sun roof controls are located, is an ideal place to add some custom controls and switches.
Although there is a sun roof motor and control box plus ACE accelerometer hidden behind the console panel, there is still lots of space to fit some more stuff. All you have to do is to plan before you start drilling in the console, so there is enough space behind it to fit your equipment.

Here is what I ended up with in my Disco:

I added the the three lamps and the right switch first some time ago and used it for the roof halogens, therefore with the second (left) switch it looks not symmetrical, but this is what it is. If you plan all of your switches and indicators at once, you will place them much more ideally.

Items added to the console:

• A switch to enable/disable roof long range lights. The long range lights are put on simultaneously when the main beam is on, but with the overhead switch you can control if it is main beam+roof or just the main beam.
• A switch to enable/disable air compressor. When enabled, it will pump the air tank and keep the pressure as set in the pressure switch, in my case 6.5 bar.
• A red push button to honk the Siberian Express horns. The button originates from Polish tractor named Ursus where it served as a signal button.
• Three control lamps: green lights when roof long range lights are operating, yellow lights when air compressor is operating and red is not connected anywhere yet. The lamps are Linrose incandescent indicator lights and I bought them at Frys in the US.
• A manometer that presents current pressure in the air tank. I put a 6mm blue PE air pipe all the way from before the horn solenoid on the compressor side of the car (using a 3 way air splitter), through the engine compartment above the engine, through the grommet to under the fascia inside the car, up under the windshield pillar's cover and under the headlining to the space behind the panel. I made a solid half-loop with the pipe and plugged it into the manometer from the right side, so it had enough length to make panel removal comfortable. The manometer is a ICH 304.40.10 0-10 BAR, fi40 mm, G 1/8.

All the wirings at the back of the panel were soldered to a connector, to make the unmounting of the console as easy as possible. 

The ignitition-switched +12V can be easily obtained from a Homelink cable, which in case of European models is not connected anywhere. It is a two-cable and two-pin loose connector, very easy to spot. The ground can be taken from there too, or from the interior lamp metal housing inside the console.

And some pictures of the console mounted in place:

Electrical Wiring

Here is a diagram of electrical connections for the roof long range lights, air compressor and horns. There are six boxes that represent different physical areas in the car, that are connected using extra wiring that was added for that purpose. The colors on the electrical lines between the boxes represent the colors of the wires that I used, so later I can figure out which wire serves which purpose.

• "Overhead panel" - the panel described above. 
• "Under fascia" - the space under the steering wheel next to the fuse box. I used a 10-wire ribbon cable between this space and the Overhead Panel, putting it along the pillar and under the headlining. On both sides of the cable I used a Molex 12-pin connector kit.
• "Engine compartment" - the space next to the engine fuse box, originally intended for storing a jack. I put an auxiliary fuse box with fuses and relays in this space. Following cables were used to connect this space to other spaces:
• 4-wire 0.5mm2 electrical cable to "Under fascia"
• 2-wire 2.5mm2 speaker cable + 1 wire 0.5mm2 electrical cable in one conduit to the Compressor
• 2-wire 2.5mm2 speaker cable to the roof long range lights
• 2-wire 0.5mm2 electrical cable to the horn solenoid
• "Roof halogens" - a mounting bar on the roof holding four long range lights (not really halogens)
• "Compressor" - a space in a right side of a rear bumper holding the air compressor with the air tank
• "Horns" - a space under the chassis floor underneath the driver's seat holding Wolo 847 horns with solenoid valve.

And some view of the jack storage space with auxiliary fuse box. The red box is a chip tuning of unknown origin added by a previous owner. It looks like a SpeedBox, but really hard to say 100%.

  

Wolo 847 Siberian Express Horn on Disco 2 - Part 1 - Horns and Air Compressor

I wanted to upgrade the horn signal to something that would sound more meaningfully. There is a pretty wide selection of horns available, but most of them are either electrical or have an integrated small blower motor that pumps the air to the horn. Nice, but not meaningful enough.

Horns

Finally, I came across this set of horns that immediately drew my attention:
Wolo 847 on Amazon or manufacturer site.

You may type the model on youtube and see how it is supposed to work. This seemed like a real 152dB set of three horns, that operate on compressed air supply and come with an integrated solenoid.
Unfortunatelly, totally not available for purchase in Europe, but you can always get it from Amazon (extra export and shipping charges of around $50).

I needed to find a right place for them to put in my Disco. In the set, as it is originally mounted, the three horns are bound together with a metal bracket that also holds the air joint screwed directly to the tubes. The solenoid valve also resides in the same joint, so it all looks clean, but the overall size of everything is hardly any practical to arrange with something smaller than a tractor. There is no way you can fit it into any part of Discovery 2 that is concealed, and I did not even consider putting them on the roof.

The only way was to dismantle them and attach each horn separately, then connect them with air pipes. Fortunetelly, after unscrewing the horns from the bracket it revealed they were connected to the 3-way joint with a short 1/8" threaded connecting pipe. It would be enough to screw on top a 1/8" female threaded fitting that later connects to a 6mm PE air pipe, like that one:

I would not screw a male air pipe fitting directly into the horn body, since horns are made of plastic and I preffered to leave the original metal connector inside the horn and not tamper with the threads that could become loose.
This way the three horns became separate and ready for attaching to some Disco body part that would fit them. They still are pretty large even separated. Struggling with finding space within front bumper or engine compartment was not successful. At the end, through experiments, I managed to fit them all on the bottom of the driver's side of the chassis. There is enough space there so they remain completely hidden and covered by the sill. The only disadvantage would be dirt and mud and water (if you wade), but I thought I could add some metal or fabric protective mesh later that would not stop the sound but prevent the dirt from getting inside the pipes.

I attached the horns with brackets directly to the chassis. You have to drill holes in the chassis to do that and to uncover a bit of the floor uphostery inside to put the screws through the chassis. This is not problematic except for the holes that go directly under the driver's seat - you should watch for the electronics located under the seat (Harman amplifier goes there) so you don't drill up to it. It is enough to remove two screws holding the amplifier at the door side and it should bend up enough to place screws below it and down to the drilled holes. The result is following:

The three air pipes coming from the horns would go to a 4-way air pipe connector, which I screwed using a large washer to a metal mounting frame visible in the middle of the first picture. I don't know what it was supposed to serve, but apparently on my car it was not used. To the same frame I attached the solenoid valve, using a metal band, and plugged it into the remaining port of the pipe connector with a short piece of air pipe. I wrapped the valve into a piece of foam insert so it does not grind against the frame. The original cable bolt connectors were cut off and replaced with a 2-pin water resistant plug, which is visible on a second picture below.

Air Compressor

It was relatively easy to find a place for the air compressor together with a small air tank. The right side of the rear bumper under the chassis had an empty space of 24cm x 40cm x 20cm (9x15x8 inches). It is next to the fuel tank, in case you run on gasoline, you may want to consider a different approach, in my case the air compressor heater even close to the tank seems to pose no danger to the diesel fuel inside.

Since the horns operate at air pressure up to 7 bar, I was looking for equipment that would handle no more than 10 bar and allow for maintaining a pressure of about 6 bar.

After some time spent on searching I decided to get following items:

• Air compressor PR656
  It is of a right size, moderately cheap, has no reduntant items like handle but has a mounting base with shock absorbers. You may get it from Chinese stores like aliexpress or alibaba, however I found one on Allegro (Poland's Internet auction site).

• 5L air tank for some truck, again from Allegro

• A second hand pressure switch FESTO PEV-1/4-SC-OD
  It is water-resistant including cable connector and has an adjustible pressure in a range of up to 12 bar.

• A 10 bar safety pressure valve

• A lot of air connectors, size reductors, etc. whatever you need to connect everything together

The compressor and tank needed to be mounted together on some kind of a frame. This way it would be easy to remove the whole set from the car in case repairs were needed. There is nothing standard that could be used here, so the frame needed to be hand soldered:

Everything put together and screwed to the frame:

A couple of things that I learned or decided when assembling it:

• The compressor comes originally with a big metal non-return valve at the end of the hose (you can see it in the air compressor product picture). At first I screwed this valve directly into the tank, but the result was a horrible rattle sound when compressor was operating. The tank acted as a resonation box amplifying the sound of a metal element moving inside the valve. Finally I got rid of the metal valve and replaced it with a small Festo HA-QS-6 non-return valve.
• I did not get rid of the original metal reinfornced hose attached to the compressor. The compressor may get pretty hot when operating and I was not sure if the PE pipe attached directly to the compressor would not suffer.
• There is a foam between tank and the frame, to mute the potential grinding

[Fix from 2017] After two years of operation, pressure switch decided to die. The metal part that is used to switch electricity, although rated for correct current, burned out. I removed the pressure switch from compressor and placed a new identical one in the engine compartment, connecting it between compressor cabin switch and relay. This way it will be exposed to minimal current, however, it will protect the circuit before the relay. Relay failure can potentially make compressor work infinitely, hoping for safety pressure valve to kick in.

Some more pictures:

Now, the frame needed to be attached to the chassis floor. To do that, four holes need to be drilled in the floor. I needed to remove completely the plastic side storage box inside the boot, as two of the screws had to be located underneath it. Also, the boot's uphostery requires uncovering in the areas of the holes, to put the screws through the holes. Having the screws positioned inside the drilled holes, I screwed them with nuts from the other side, so there is no need to remove anything from inside the boot again, in case the compressor must be removed. On the nuts, went the frame, and washers and nuts again, to finally attach it to the chassis.

You may notice on the air compressor pictures above, that there is a round intake air filter attached to the compressor body (below the radiator). Where the compressor is located now, there may be a chance of water getting into the filter, which may be destructful to the compressor. So it may be a good idea to source the air from some point located higher than the compressor itself. I did not do it at first, but later decided to change it and reuse an air filter coming with the original Land Rover air suspension compressor, which I removed some time ago, replacing the suspension air bags with springs. The air filter was located behind the rear lamps inside the fender. I reused it, just changing the side of the car it was installed, to the one where the compressor now was. With some air connectors, I managed to attach the original hose from the air filter, through some extension, to the compressor's air intake. Original round filter of course had to be removed and disposed of.
Here is a view of the new-old air intake filter and how it is attached to the compressor body:

Now connect the compressor outlet pipe to the solenoid inlet and you are ready (almost - still need to add some electrical wires).

Please check other posts for:

• Overhead control panel and electrical wiring
• Tyre Inflation Air Port

My Disco 2

This is my dearest year 2000 2.5TD Land Rover Discovery 2.
I bought it in 2012 and it serves me beautifully since then.

I am going to write up some of the mods and upgrades that I am doing to it.
For now, this is what it looked like in December 2012:

It came on 18" black alloy wheels which looked pretty cool, although it could fit only standard highway tyres.