My P6 isn't very 'horny'!

Phil Robson

Phil Robson

Well-Known Member
Many of you may have had the problem where at least one of your car's horns doesn't work. With BOP it's the Low tone, which means the sound is rather feeble for a car with such presence!

It's difficult getting 2nd hand Low horns off the likes of ebay & I don't want to spend £100 on a NOS one if I can repair the existing one (always more satisfying of course). I have tried a newer (part plastic) horn, but it sounds more like my daughter's Fiat 500 :rolleyes:

I thought I'd have a look inside, so I ground off the rivets:

IMG_7196.JPG

This is what's inside:

IMG_7200.JPG

I'm no good at electrics at all, but they seem to be basically a diaphragm with a metal rod inside a coil. When the current passes the electric field forces the rod upwards which in turn operates a switch (contact breaker) that disconnects the current & the diaphragm returns to its normal state, to start the process again a very-many times a second, giving the vibration that is amplified through the 'trumpet'.

There is an adjustment screw which appears to be for tone (it will change the length of time the switch stays closed hence the number of vibrations per second) & a top adjuster that seems to alter the maximum travel of the diaphragm.

Here is the switch (corroded in this case):

IMG_7201.JPG

I've cleaned the switch up nicely but can't get the horn to work when connected across a battery :( Surely, it can't be that difficult, but it's beyond me at the moment.
 
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I have repaired successfully those Lucas horns in the past. I have removed the rivets, disassembled, cleaned and painted as necessary, and assembled again using small nuts and bolts. When you connect the horn to a battery at least you should hear the coil pulling the diaphragm. You don't need to play with the diaphragm travel, but if the switch adjustment is way off, the horn won't work. Then you adjust the switch until you have the horn sounding loud and clear. If the coil doesn't pull the diaphragm, you should check the coil and the switch with a multimeter, obviously with the horn disassembled.
 
How freely is the core in the coil moving? It’s basically a solenoid so if it sticks that cause issues. If I’ve freed mine off with wd40 and patience in the past.
 
sdibbers said:
How freely is the core in the coil moving? It’s basically a solenoid so if it sticks that cause issues. If I’ve freed mine off with wd40 and patience in the past.
Click to expand...

I thought the core was the part fastened to the diaphragm, in which case it moves easily... Am I wrong?
 
Demetris said:
I have repaired successfully those Lucas horns in the past. I have removed the rivets, disassembled, cleaned and painted as necessary, and assembled again using small nuts and bolts. When you connect the horn to a battery at least you should hear the coil pulling the diaphragm. You don't need to play with the diaphragm travel, but if the switch adjustment is way off, the horn won't work. Then you adjust the switch until you have the horn sounding loud and clear. If the coil doesn't pull the diaphragm, you should check the coil and the switch with a multimeter, obviously with the horn disassembled.
Click to expand...


By switch adjustment do you mean the small screw?
 
Demetris said:
I have repaired successfully those Lucas horns in the past. I have removed the rivets, disassembled, cleaned and painted as necessary, and assembled again using small nuts and bolts. When you connect the horn to a battery at least you should hear the coil pulling the diaphragm. You don't need to play with the diaphragm travel, but if the switch adjustment is way off, the horn won't work. Then you adjust the switch until you have the horn sounding loud and clear. If the coil doesn't pull the diaphragm, you should check the coil and the switch with a multimeter, obviously with the horn disassembled.
Click to expand...

That is a great guide to horn repair :cool:
 
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