12 v horn problem

[Greg & Jax]

Hi all .

Over the years I've had a few 12 horns on the boat all tend to go faulty after awhile . 

I have bought a new low current 12 v horn from China cheap stainless steel  one .

I have checked there is a 12v feed on the end of the cable but when I connect the horn it doesn't work .

Yet if I take the horn to the battery and connect them direct  it goes off like a mad thing . 

The end of the cable is about 50 ft away at the front of the boat . 

Any ideas why this would be ? 

I would be greatfull for thoughts on this 

Regards Greg. 

Edited May 29, 2020 by Greg & Jax
Fat fingers

[WotEver]

3 minutes ago, Greg & Jax said:

Hi all .

Over the years I've had a few 12 horns on the boat all tend to go faulty after awhile . 

I have bought a new low current 12 v horn from China. 

I have checked there is a 12v feed on the end of the cable but when I connect the horn it doesn't work .

Yet if I take the horn to the battery and connect the two wires it goes off like a mad thing 

You have a poor connection somewhere on the horn feed. You need to be checking the voltage with the horn connected (yes, I know that means two of you), as a feed with no load can give misleading results. As you’ve found. 
 

Look for corroded connectors or even a faulty horn push. 

[Jen-in-Wellies]

Likely a dodgy high resistance connection in the wiring through the boat somewhere between the battery and the horn. You say you've checked there is 12V at the end of the cable. If you connect the horn and measure the voltage across it when the button is pressed you will probably see this drop to only a few volts. If so, then it is a matter of going through each connection to fuse, button, etc to find the duff one. Another possibility is that the wire is too thin, but if horns have worked before, then this is unlikely.

 

Post clash with @WotEver!

 

Jen

Edited May 29, 2020 by Jen-in-Wellies

[Greg & Jax]

Hi guys thanks for the reply,s .

The other horns where not as loud as this one seems to be . 

I've connected the horn at the far end and my wife pushed the button for me reading was 12.6 when she released the button the reading was back to zero 

But still no sound . 

Cheers guys .

[Tony Brooks]

If that reading was with the horn connected with good tight connections then to me it suggests a faulty horn.

[WotEver]

2 hours ago, Greg & Jax said:

if I take the horn to the battery and connect them direct  it goes off like a mad thing . 

 

23 minutes ago, Greg & Jax said:

I've connected the horn at the far end and my wife pushed the button for me reading was 12.6

 

That's impossible unless the horn became faulty between the stern and the bow.  Were you reading the 12.6V across the connections to the horn? There's no point reading it anywhere else.

[Greg & Jax]

Hi guys .

I connected the horn but didn't cover the terminals  I had my meter on them .

Got my wife to press the horn .

12.6 . But no sound . 

Take horn back off connect it direct to battery  the horn  is real loud .

Got me a little disconbobulated he he .

Cheers 

[NewCanalBoy]

Was the ignition on ?

[WotEver]

11 minutes ago, Greg & Jax said:

Hi guys .

I connected the horn but didn't cover the terminals  I had my meter on them .

Got my wife to press the horn .

12.6 . But no sound . 

Take horn back off connect it direct to battery  the horn  is real loud .

Got me a little disconbobulated he he .

Cheers 

Re-check those connections at the horn end.  If it works it works, and the only reason it won't work is if the connection is faulty.

[Mike Adams]

Longshot but there might have been enough current to open the contacts and hold them open just but not enough to get it in vibrating mood. Measure the current going into the horn when it is connected but making no sound. No current and 12.6v should be the same as connecting directly to a battery. They will take large pulses of current when operating.

[WotEver]

 

Just to be clear...

12 minutes ago, Greg & Jax said:

12.6 . But no sound . 

Take horn back off connect it direct to battery  the horn  is real loud

Is impossible

1 minute ago, Mike Adams said:

Longshot but there might have been enough current to open the contacts and hold them open just but not enough to get it in vibrating mood.

If that were the case then the voltage would have collapsed.  It's a dodgy connection right at the horn I believe.

[dmr]

Some horns are very sensitive to voltage, maybe cheapo chinese are even more so. Older horns sometimes had an adjusting screw, maybe yours does but I doubt it.

I suspect the volt drop down your wires is just too much for.

 

Years ago I fitted a cheap horn to my VW camper and it would only work when the engine was running.

 

You get what you pay for. Get a nice big vintage Klaxon ?

 

..................Dave

[Mike Adams]

10 minutes ago, WotEver said:

If that were the case then the voltage would have collapsed.  It's a dodgy connection right at the horn I believe.

Without knowing the actual construction of the horn one cannot be sure but if he is measuring 12.6v on the actual horn terminals then it can't be a bad connection unless it has some electronics in it that is shuting it down. Probably too much resistance/inductance to get the peak current it needs to resonate.

[WotEver]

4 minutes ago, dmr said:

Some horns are very sensitive to voltage, maybe cheapo chinese are even more so. Older horns sometimes had an adjusting screw, maybe yours does but I doubt it.

I suspect the volt drop down your wires is just too much for.

I guess that's possible.

 

OP - does it make any kind of noise when the horn button is pushed?  A clunk or anything?

1 minute ago, Mike Adams said:

Without knowing the actual construction of the horn one cannot be sure but if he is measuring 12.6v on the actual horn terminals then it can't be a bad connection unless it has some electronics in it that is shuting it down. Probably too much resistance/inductance to get the peak current it needs to resonate.

You keep saying this.  If that were the case, the voltage would collapse.  E=IR and all that.  12.6V should be enough to sound the horn unless it's faulty.

 

OP - another question: what's the voltage at the battery terminals?

[Tony Brooks]

What type of terminals - if they are blades the OP may have the meter on the outside of the female connector with a bad connection between that and the blade.Likewise if its a nut and stud connection if he has his meter on the eye terminal and not the stud. Could even be a bad connection in the horn and its just coincidence that moving to the back of the boat allows it to make a good connection.

Edited May 29, 2020 by Tony Brooks

[WotEver]

1 minute ago, Tony Brooks said:

What type of terminals - if they are blades the OP may have the meter on the outside of the female connector with a bad connection between that and the blade. Could even be a bad connection in the horn and its just coincidence that moving to the back of the boat allows it to make a good connection.

Yup.

[Mike Adams]

Ok assume it is a 'old fashioned job'. You need two components to make it work ie resonate. The contacts are closed at the start, a pulse of current flows into the coil, which moves the steel disc and opens the contacts. The steel disc is tuned to resonate at the horn frequency continually opening and closing the contacts at that frequency. Successful operation relies enough current in the coil to start the process going. That current is a function of the voltage applied and the resistance/inductance of the whole circuit. If the current cannot rise or fall fast enough it may not function even though the applied voltage is sufficient. The only way around this is to reduce the resistance of the cable.

[dmr]

4 minutes ago, Mike Adams said:

Ok assume it is a 'old fashioned job'. You need two components to make it work ie resonate. The contacts are closed at the start, a pulse of current flows into the coil, which moves the steel disc and opens the contacts. The steel disc is tuned to resonate at the horn frequency continually opening and closing the contacts at that frequency. Successful operation relies enough current in the coil to start the process going. That current is a function of the voltage applied and the resistance/inductance of the whole circuit. If the current cannot rise or fall fast enough it may not function even though the applied voltage is sufficient. The only way around this is to reduce the resistance of the cable.

I was just going to say that, but you not only got in first but also said it much better.

 

...........Dave

[Tracy D'arth]

Could  this new horn have some electronics inside which is polarity conscious?  Otherwise its a bad contact right at the horn connections. Try it with a car headlamp bulb instead of the horn.

TD'

[Greg & Jax]

Thanks for all the reply,s .

I will have a good look round it later when I'm home and do some of the things you all suggested 

Thank you for the help and insights 

Cheers Greg. 

Ice just contacted the seller and the horn is a 12 v low current . 150 watt horn .

Edited May 29, 2020 by Greg & Jax

[WotEver]

.

Edited May 29, 2020 by WotEver

[WotEver]

45 minutes ago, Mike Adams said:

If the current cannot rise or fall fast enough it may not function even though the applied voltage is sufficient and the voltage will collapse.

Corrected that.

 

By your logic voltage and current are unconnected.  They're not.  If the device (horn in this instance) attempts to pull the required current but is unable to because of resistance in the circuit then the voltage will be pulled down as determined by the circuit resistance and the current flowing. 

 

Put a 12W lightbulb in a 12V circuit with a 24r resistor in series.  The lightbulb wants to pull 1A, meaning it has a resistance of 12r (ignore the thermal resistance change for this example). The voltage seen across the bulb will be 4V.  It won't be '12V with insufficient current', that's not how Mr Ohm's rules work.  No different with the horn, if it can operate at 12.6V and it is receiving 12.6V then it must operate unless it's faulty.

 

17 minutes ago, Tracy D'arth said:

Could  this new horn have some electronics inside which is polarity conscious?  Otherwise its a bad contact right at the horn connections. Try it with a car headlamp bulb instead of the horn.

TD'

Good test.

 

 

Edited May 29, 2020 by WotEver
typo

[ditchcrawler]

6 minutes ago, Greg & Jax said:

Thanks for all the reply,s .

I will have a good look round it later when I'm home and do some of the things you all suggested 

Thank you for the help and insights 

Cheers Greg. 

Ice just contacted the seller and the horn is a 12 v low current . 150 watt horn .

Yes that is not much over 12 amp, I wonder what else on a boat draws that sort of current

[Mike Adams]

1 minute ago, WotEver said:

Put a 12W lightbulb in a 12V circuit with a 24r resistor in series.  The lightbulb wants to pull 1A, meaning it has a resistance of 12r (ignore the thermal resistance change for this example). The voltage seen across the bulb will be 4V.  It won't be '12V with insufficient current', that's not how Mr Ohm's rules work.  No different with the horn, if it can operate at 12.6V and it is receiving 12.6V then it must operate unless it's faulty.

Unfortunately it is not as simple as this. Assume the horn is operating at 1KHz. This means that you are dealing with an alternating current at 1KHz. It is not a simple dc set such as you have described, and the waveform will have current components at higher frequency than the 1KHz mainly 3rd and 5th harmonics. These components will be subject to any inductance or capacitance in the circuit and the circuit will behave differently.

[WotEver]

Just now, Mike Adams said:

the circuit will behave differently

And certainly wouldn't show 12.6V DC on a multimeter if that were the case.