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Horns, Fixing

Horns, Fixing

To All: Does anyone have any experience with getting XK140-style horns into working order? Both of mine are dead, so I took them apart for a look. The internal parts appear intact and show no sign of deterioration except for a little oxidation on the electrical contacts. Now they will grumble a little when 12 v. is applied to the terminals. Any advice will be appreciated. - Sam Bell '57140

If they grumble, then they should only need adjusting. I presume you have found the screw which adjusts the contact pressure. With power applied to the horn, turn the screw a couple of turns in and out, and you will probably find that the horn springs into life. Leave it blowing for a few seconds to bed and clean the contacts, and then adjust for the cleanest note. Also ensure that it starts reliably at the final setting. Use them regularly to keep the contacts clean. - regards, Mike Morrin

Sam, I can't help with fixing the horns, but I would like to know if your have any markings stamped etc on them, and what colour they appear to have been originally. - Regards, John Elmgreen

Mike, Thanks for your info. I did ID the adjustment screw. The horns do grumble, but only when I "tickle" the bullet connector sockets with one of the 12 v test leads from a battery. There's no activity if I simply attach the leads. Seems like the problem is probably in the contact points. Please let me know if you have any other suggestions. - Sam Bell

Sam, Electric horns are all very simular in design. The horn functions by utilizing an electro-magnet which is controlled by a variable switch (the point contacts). When you beep the horn the circut is completed to the horn energizing the electro-magnet, which is pulsed by the points.The pulsed electro-magnet vibrates an iron shaft, which has a diaphram attached to it. The tone adjustment screw changes the dwell of the point contacts, which causes the tone of the horn to change. Besides dirty or worn contact points, I have found that rust build up on the iron shaft will cause a drag that the magnet cannot overcome. Make sure that the shaft is not sticking if it is you will have to disassemble it further. Also make sure that the electromagnet is still functioning. - Regards, Wray Schelin

John, The horns are painted black. They are disc-shaped, 5 1/8" diameter, 6 screws hold the outer ring to the body with the diaphragm and 2 gaskets clamped between. 2 of the screws are long bolts with nuts that attach the horn to a spring-steel mounting bracket. Markings on the outer rim : LUCAS Markings inside the body: 70355 FR6. No markings on the diphragm. A tag is attached to the 2 mounting bolts. One of those tags is marked "12v 70071E 10 56" ; the other is marked 12v 70063E 10 56" Maybe the tags indicate the different pitches, and maybe 10 56 is the date of manufacture. - Sam Bell, '57 140 FHC

Sam, Great work, thanks for the horn description. Any sign of anything other than black paint? Grey/green perhaps? I ask because the JCNA (p 44) says horns were grey, and the Lucas book says they were "polychromatic grey". As to whether part was black, the illustration in the Lucas book shows it all grey, quite a light grey in fact. But still we have one or two reports of black and as it is such an easy repaint colour, I do not know if they are original. Your part nos. are correct by the way. - Regards, John Elmgreen

John, I am quite certain my FHC horns are original. They both sport the gray "polychromatic" (whatever that implies) paint coating and, by the way, don't work either. Regards - Klaus Nielsen

John, These horns are quite worn with the base metal showing through, but when cleaned they are clearly painted plain black. There's no sign of gray paint or even primer - only the oxidized light gray of pot metal where the paint is worn or chipped away. - Sam Bell

Wasn't it only the 140 that had grey horns? Didn't we go through this question once before when we were chatting about horn pitches? I couldn't find it in the archives.

My 120 and MkV horns were original black all over. They painted the dome separately. One of my domes had a big unpainted bubble inside, I imagine because they didn't spray it, they hung it on a wire and dipped it in a bucket of paint. Then they put it on the horn and painted over the whole thing. - Rob Reilly

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