One of the best thing about early Falcons is they're nice and solid even the original horn sounds solid when compared to the pathetic squeak of a modern car. Also unlike a modem car the horn can be serviced and it's pretty straight forward, here's how they work.
When a voltage is applied to the horn, two electro magnetic coils pull down a soft-iron bar which is suspended from a thin metal diaphragm.
Attached to the opposite side of this bar is a piece of U shaped channel which pushes away the lower of two contacts.
This results in a break to the flow of current in the coils which releases the bar, diaphragm and contacts to return to their original position.
The contacts are now closed and providing a voltage is still being applied to the horn the coils will pull down again, release and so on.
This make and break action causes the diaphragm and the volume of air within the horn throat to oscillate, which in turn generates the sound.
Cross section of the RVB Windtone Horn typical of XM XP
It's the same old story with contacts, like ignition points they just hate it when the sparks, fly. Most times they get pitted, some times they get stuck together. Either way they can normally be fixed up with a bit of clean.
Firstly, file a mark across the join between the horn to assist with the rebuild. Then with a wire brush and CRC clean the bolts threads before attempting to remove the nuts. Very Important! The bolts have domed heads with a very small shallow square shoulder. The minimum of slippage caused by, tightness will round this shoulder or the square holes in the die-cast body! Tackle the nut in the mouth of the horn first, apply lots of pressure to the dome part of the bolt to keep the shoulder well in contact with the hole If you can't. get this one out you can't Get inside! Once all the nuts are off split the two halves and clean the throat side and diaphragm which is then lightly smeared with grease.
Then un-solder the coiled shunt at each eyelet and swing it out of the way, of the nut below. Make a note of where the two wire come and go from, plus the approximate depth of the adjuster bolt, before it and the nut revelled below the shunt, are removed.
Extreme care must he taken to note the order and position of washers, insulators and spacers removed from the contact terminal during dismantling! Only then should the contacts be removed and cleaned. It may he worth drawing a diagram, as one shown here may not be the same as your horn!
Contacts and the insulators around the contact terminal
Re-assemble in the reverse, order starting with the contact terminal, shaft insulating sleeve. Slide all other insulators, washers, etc. over the sleeve making sure none come in contact with anything they shouldn't. Replace the adjuster bolt to the original depth and blot up.
Apply 12 volts positive to the spade terminal and ground the horn body to negative while rotating the adjuster bolt to start the horn and give the best sound.
© BigH 1997
DISCLAIMER
While this method has been tried and works, NO responsibility will be excepted by the Author, the Club or any of its Members.
