Jaguar Windtone horn

I have a Windtone 'H" horn that I cannot understand the fault condition

It was in need of a complete strip down, I did verify that after cleaning the points, it did make a sound, meaning the coil worked, prior to taking it completely apart

When I put it back together, it no longer works at all, and I suspect the coil has gone either open or short circuit, but I cannot see, or understand how the coil is wired

I have an open circuit between the body (which has an earth wire), and the voltage input terminal/s with the points closed, and verified conducting

The following 2 pic will illustrate further test

There are two brass receiving terminals, which connect to the red and black wires

I cannot tell from visual inspection where those enter the coil, but as the reading with or without the points closed is 0.4 Ohms, so I am going to have to assume that what I have is an open circuit of the coil to the horn body ?

So I had another go at this Windtone WT618 "H"horn

I believe it is the same as in XK120, this one was from a '51 MK7, and had been lost in pieces deep in my garage, so due to its fine decor look, I was loath to throw it away

turned out my dumb, as when I inspected it under good light and magnification, I could see the wires went to each coil end, and this time it measured about 3.0 Ohms, suggesting a coil resistance of ~2.7 Ohms

I observed that the end of the positive and negative terminal are within 1/8"of my each other, and my probe had probably slipped down to short the circuit…it looks like in the pic

So that brings me tho the wiring. It has two wires running inside connected to each terminal, and a separate earh wire on the mount ( as pictured)

The separtate earth wire appears to searve no function, as it is electrically insulated from the other two terminals insides

I have two wires emerging from the dome, and they are activated, sounds very loud

Thing that’s got me fooled is felt certain I had “tested” it before resto by applying 12v to earth wire/body, and one terminal, so unless i put it back together wrong, I must be dreaming

Do XK120 owners have one or two wires emerging from bowl grommet ?

here is how it went together

This horn was in poor condition

taking them apart is easy, I soaked all parts ib CLR for a few days, then painted and lubed all parts

The points need to be drawn across a points file, they arc a lot, and pull big current, up to 10A

Once I had it all working beautifully, I decided to panel beat the dents and creases out of the bowl, did a pretty good job, file finished it sand, etch & prime, the alloy is not conducive to paint adhering wel

It is a appreciably louder than the smaller OEM 420G horns, which I am just overhauling as well

Evey one I have come across has points failure, which can be revived with a file, or eveb wet & dry in most cases


Two wires is correct. One to each side on the terminal block.
The extra grounding wire on the body is not necessary.

They are not polarity sensitive.
They are generally wired with a wire on one side to ground, and another on the other side to a relay, which connects to a negative source when the horn button is pushed.
Although they can be wired the other way, the horn button connecting to ground, as on my '38 SS.
There are several styles or designs of the bell trumpet. One is round, one is like a teardrop, and one is almost square.
I like the tone, it is like a French Horn, rather than some smaller horns which sound like a Piccolo Trumpet.