If you own a late model Mercedes Vito 2004-on (W639) you will no doubt be fully aware of how poor the horn is compared to other medium sized commercial vehicles and most other cars on the road!.
This can be easily remedied by installing better horn sounders – a trip to the local scrap yard will produce the goods at a very low price. Sure, you can buy off-the-shelf horns from accessory shops but rarely are they of the quality of OEM units, often made by top manufacturers like Klaxon, Hella or Fiamm. When you get to the scrap yard look for high end saloons and estates, BMW, Jaguar and Audi being the most common producers of quality dual horns. Always identify the ‘scroll type’ horns in preference to the feeble disc horns that are common these days, look for good clean examples, there will be plenty to choose from. The scroll type horn produces a loud and full tone, a Hi-Lo tone pair will when fitted, scare most motoring offenders out of play!
I secured my pair of horns from a BMW 5 series, manufactured by Klaxon and both very clean indeed, they cost £5 for the pair and I would imagine cost in the region of £70-£80 off the shelf. I cut the wiring looms back as far as possible when removing them from the donor car so that I could fully utilise the attached wiring and their waterproof plug and socket type power connectors.
Fitting was easy. Lift the bonnet, remove the three screws on the top of the grille, un-slot it and remove it up and out from the Vito. Locate the two plastic moulded grey ABS brackets either side of the radiator that support the front bumper skin, position your horn on the inside of these brackets and check the fit. Drill a suitable hole through the plastic bracket and fix the horns either side – note there is a great deal of room behind the grille if its a model without air conditioning. You will probably have to be a little more inventive with the mounting location if you are restricted by the air-conditioning condenser and its cooling fans, it would probably be good practice to check clearance by refitting the grille before committing to a mounting place. However it is an easy job to mount the horns in this area.
Once you have mounted the new horns, wire them both in parallel and route the two connecting wires through to the drivers side headlamp unit (Right Hand Drive). Stretch your arm down behind and below the headlamp unit and you will find the original single disc type horn, feel for the connector and unplug the lead feeding it back through to the engine compartment. Splice in your new horn wires to the original horn connector, tape up the joints and tie wrap the cables neatly out of the way. Test your horns and refit the grille assembly. If you would like to hear the resulting sound of fitting the dual tone horns, just select the W639 horn sound track in the Mercedes Sounds player to your right and click play.
Job Done !