Getting the Horn

[ShipsWoofy]

My horn died, it was one of these, though mine was from a jumble, below is the force4 own brand, mine seems to be identical.

I want another, there appears to be the type as above, or the more expensive afi variant as below.

A couple of points, the sound out of the one I have/had, is like a mini horn, quite puny, but good enough to warn the odd dinghy I am approaching.. is the AFi a better horn? I have the horn mounted under the radar up the mast and so the mobo long horn types are out of the question.

Just before I spend more money on the damn boat..

how do these things work and if I break it open can much be done to a dead one?

Thank you in advance..

 

[Dave_Seager]

In my experience, these horns can often rust away internally. If you open the cover that will be obvious and you will need a replacement. I cannot comment whether EFI is a better horn than what you have.

If the horn appears to be in good condition then check that it is getting 12v. If so, then there is usually an adjusting screw inside. This is often sealed with paint or mastic and may have a plastic cap on it. These are all intended to deter you from touching it but if it does not work already you have nothing to lose.

Try turning the adjuster about half a turn in either dierction to see if it makes any difference. It adjusts the position of one of the contacts inside. It needs to make contact when the horn is off but as soon as the coil is energised and the diaphragm starts to move it should break contact so that the diaphragm returns and makes contact again. If it is out of adjustment then either no current passes at all or the coil stays on all the time. In the latter case you may hear a click or pop as you press or release the horn button.

I have twin horns on my boat and they stopped working this season. One contact was staying closed, stopping that horn from working. However, it also drew so much current that the other horn did not work either. Adjusting twin horns is more difficult as you need to test them and adjust them separately. However, I was able to get mine working after a while by adjusting the contacts as described.

 

[ShipsWoofy]

There was a fair amount of flaky rust under the ss cover, I tapped it vigorously with 12v connected, to no avail, although rusty, there did not appear to be any collapsed metal.

I did see the adjustment screw but did not touch it (I had no idea what it was for). I will have a play with that later. Thank you for advice, as you say, nothing to lose.

 

[elton]

Somewhere in there there'll be a pair of contacts that are pulled apart by an electromagnet (breaking the circuit to the electromagnet and thus allowing the contacts to touch again). You need to clean the contacts. First try inserting a bit of cardboard between them, and drag it back and forth. If that doesn't work, try a bit of fine wet-and dry folded in half (so it's rough on both sides). Whatever you do don't bend the contacts, and don't make adjustments to any screws unless nothing else works.

 

[savageseadog]

Thought it was a porn thread!

 

[Cliveshep]

These horns universally work by a make and break contact flexing a metal diaphraghm which is attached to an iron core moving inside a coil. Power energises the coil which pulls in the soft iron core, at the same time breaking the circuit, the magnetic field collapses and the core springs back into position closing the contact which thus energises the coil again and so on. Adjustment is provided which tunes the frequency to get the most noise out of the system and is NOT provided for you to play with when the horn quits working!

Two things can go wrong assuming your horn butten and associated wiring are working correctly and power is getting through to the horn.

Firstly, the contact points can become dirty or corroded, cleaning them will restore electrical efficiency but inevitably you will later have to re-tune with the adjuster screw. A spray with a contact cleaner or switch cleaner may save you scraping the contacts with emery cloth which is really stage two of work in this area.

The second problem is that the iron core has rusted to the extent that it can no longer move freely inside the coil, i.e. rust has expanded it and it is plain sticking. Here emory cloth will solve your problem and a light oil thereafter before assembly should complete your overhaul.

Of course, if the coil is burnt out the other thing to do is get hold of a large iron frying pan and beat it vigorously with a metal ladle! It makes a loud noise and also is quite cathartic as you can release pent up frustration!