My twin horns now sound like a single mouse?

[Mike k]

I have a pair of nice horns which worked fine ( probably used twice in a year) but last weekend whilst we were having a motor around my son asked what they sounded like... I pressed the rubber button on the helm and nothing. Got back to berth and rotated the button a coupe of times back and forth and we then got sound again. Because it niggled me slightly ,yesterday ( a week later) decided I would investigate further to check all connections behind the panel but they all seemed fine and I managed to get yesterday a single sound from just one horn and nothing from the other.
The sound was rather pathetic but it may be ok coz I have never heard just one horn before I think they operate twin sounds .

Any suggestions would be welcome .

Many thanks

Mike

 

[chrisbitz]

maybe run a jump wire directly form the battery to the horns? I've heard that sound on a car with a bad connection...

Or alternatively, remove the foreign object from inside the horn?

 

[sarabande]

spiders inside ? A bit of dis-assembly needed to see if the diaphragm is blocked/broken. I s'pose you could check that there is leckky going to them first, though.

 

[MASH]

Elininate bad electrical connections as suggested above, if all OK have the back off the horns, I bet you'll find the diaphragm is rusted up or otherwise restricted. There is likely to be an adjusting screw in there too that bears against the diaphragm - that might need tweaking too.

 

[Mike k]

thanks -will check the leccy to the horns first before disassembly so............... each horn has two thin black wires going to them so if I slice a little into the casing of each wire per horn and put the probes into each wire and press the horn button should I get a 12v reading on the meter and does it matter which wire I put the pos/neg probes into?

p.s Sarabande hows the lambing gone /going?

 

[Trundlebug]

You don't describe which type of horns you have, other than that they're "nice" but if they're the electrically operated stainless trumpet type with diaphragms then inoperation after a period of inactivity such as winter is quite normal.

Fixing and details as follows. Best to have a multimeter handy.
Providing you still have 12v getting to the horns, showing the problem to be at the horns not the switch or supply, the best bet is to remove them to work on in a comfortable place inside.
Remove the screws around the rim that hold the diaphragm in.
The diaphragm (if it's anything like most of them) should be s/s so ignore the comments about it being "rusted up".
On the back of the diaphragm there is a steel plunger that opens and closes a set of contact points very quickly to create the oscillation that causes the noise.

The contact points get oxidised over the winter and / or in damp conditions, which stop the horn from working.
Rub a small piece of fine sandpaper (ideally alu oxide) or wet & dry paper (used dry) between the contacts until the resistance across the points can be measured in single figure ohms. Approx. 4-8 ohms is about right. If you're getting more than 20 ohms (I've seen up to 1M ohms, effectively open circuit) the contacts need cleaning.
This is quite fiddly and requires some patience, but until you achieve it the horn won't work.

Once achieved, seal the gasket around the diaphragm with a smear of grease, and give the insides of the horn around the coil and contacts a quick squirt with WD40 to keep damp away.
Reassemble and enjoy the noise.

Usually works for 12-24 months depending upon amount of use, thereafter repeat the above.

You should NOT need to tweak the tone adjustment.

Edit: it doesn't really matter which way round you connect the wires, or the multimeter.
If your multimeter reads -12v you've connected up the probes the wrong way round but it doesn't matter - it's still showing there is voltage getting to the horn which is the important thing.

 

[Mike k]

You don't describe which type of horns you have, other than that they're "nice" but if they're the electrically operated stainless trumpet type with diaphragms then inoperation after a period of inactivity such as winter is quite normal.

Fixing and details as follows. Best to have a multimeter handy.
Providing you still have 12v getting to the horns, showing the problem to be at the horns not the switch or supply, the best bet is to remove them to work on in a comfortable place inside.
Remove the screws around the rim that hold the diaphragm in.
The diaphragm (if it's anything like most of them) should be s/s so ignore the comments about it being "rusted up".
On the back of the diaphragm there is a steel plunger that opens and closes a set of contact points very quickly to create the oscillation that causes the noise.

The contact points get oxidised over the winter and / or in damp conditions, which stop the horn from working.
Rub a small piece of fine sandpaper (ideally alu oxide) or wet & dry paper (used dry) between the contacts until the resistance across the points can be measured in single figure ohms. Approx. 4-8 ohms is about right. If you're getting more than 20 ohms (I've seen up to 1M ohms, effectively open circuit) the contacts need cleaning.
This is quite fiddly and requires some patience, but until you achieve it the horn won't work.

Once achieved, seal the gasket around the diaphragm with a smear of grease, and give the insides of the horn around the coil and contacts a quick squirt with WD40 to keep damp away.
Reassemble and enjoy the noise.

Usually works for 12-24 months depending upon amount of use, thereafter repeat the above.

You should NOT need to tweak the tone adjustment.

Edit: it doesn't really matter which way round you connect the wires, or the multimeter.
If your multimeter reads -12v you've connected up the probes the wrong way round but it doesn't matter - it's still showing there is voltage getting to the horn which is the important thing.

Thanks Trundlebug for the detailed response and for the edit . The horns are as you described - Twin S/S trumpet . Pardon my ignorance but how do I measure the resistance and is it done with power being applied to the horns?

 

[Trundlebug]

Using your multimeter, set the dial to ohms. There's usually a choice of 20, 200 or 2M so choose 20.

Using the probes on your multimeter, (It doesn't matter which way round red or black) put one so the probe end touches where one feed wire terminates, and the other where the other wire terminates. On to a soldered joint, or spade connector, or whatever.

It's important to make sure the end of the probe is touching a conductor - i.e. something metal where the power flows. Be careful with this, sometimes you need to scratch the surface a bit with the end of the probe to ensure if there's an invisible clear coating you've scratched through it to touch metal underneath.

You'll probably need to press reasonably hard and steadily to ensure a good contact, as a light touch isn't normally enough.

Once you're holding the probes in place, read off the figure from the multimeter. If it's off scale or more than 20, the contact points need cleaning as described.

It can be helpful to have an assistant steady the parts because you sometimes need more than 2 hands, at least until you've mastered how to do it.

Because the power to measure the resistance comes from the multimeter's internal battery you don't need any external power supplied to the horns when you do this.

 

[Mike k]

Using your multimeter, set the dial to ohms. There's usually a choice of 20, 200 or 2M so choose 20.

Using the probes on your multimeter, (It doesn't matter which way round red or black) put one so the probe end touches where one feed wire terminates, and the other where the other wire terminates. On to a soldered joint, or spade connector, or whatever.

It's important to make sure the end of the probe is touching a conductor - i.e. something metal where the power flows. Be careful with this, sometimes you need to scratch the surface a bit with the end of the probe to ensure if there's an invisible clear coating you've scratched through it to touch metal underneath.

You'll probably need to press reasonably hard and steadily to ensure a good contact, as a light touch isn't normally enough.

Once you're holding the probes in place, read off the figure from the multimeter. If it's off scale or more than 20, the contact points need cleaning as described.

It can be helpful to have an assistant steady the parts because you sometimes need more than 2 hands, at least until you've mastered how to do it.

Because the power to measure the resistance comes from the multimeter's internal battery you don't need any external power supplied to the horns when you do this.

thanks very much- that is a great description

Cheers

Mike

 

[MASH]

ignore the comments about it being "rusted up"....


...The contact points get oxidised over the winter and / or in damp conditions,

So - don't listen to people suggesting it may be rusted up cos it can't be, just clean off the rust... whaaat???

 

[grumpy_o_g]

Because the power to measure the resistance comes from the multimeter's internal battery you don't need any external power supplied to the horns when you do this.

I'd just amend that to read "Because the power to measure the resistance comes from the multimeter's internal battery you shouldn't have any external power supplied to the horns when you do this." as it may blow up your Mulitimeter...

 

[Trundlebug]

... I bet you'll find the diaphragm is rusted up or otherwise restricted. ..

So - don't listen to people suggesting it may be rusted up cos it can't be, just clean off the rust... whaaat???

A stainless steel diaphragm can't be rusted up. I didn't say clean off the rust - read my post again.

Electrical contact points don't get rusty, as they're not steel but tungsten or an alloy with similar properties.
They do however get oxidised through arcing and dampness which affects their electrical conductivity, as described.

If you had ever taken one of these horns apart, and understood how they work, you would know what we're talking about here.

 

[Leonidas]

Elininate bad electrical connections as suggested above, if all OK have the back off the horns, I bet you'll find the diaphragm is rusted up or otherwise restricted. There is likely to be an adjusting screw in there too that bears against the diaphragm - that might need tweaking too.

I had a similar problem which I solved by taking the horn apart, free the rusted membrane with plenty of WD40. Now it works as new (until it seizes up again- but I know the drill now !)

 

[MASH]

Leonidas, but you can't have done!

trundlebug says they don't and can't get rusty and he clearly knows everything about everything including that you and I have never taken a horn apart so he must be right and we must be wrong.

gawdelpus!

 

[John100156]

External power to the horn(s) GoG - wouldn't that be a little noisy....... mind you if you can get SWMBO to do the resistance test then wait by the horn push-button it could be fun..... ;-)