Horns blowing fuse

rafiki_

rafiki_

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I have a problem with Rafiki's horns. Replaced the fuse last time out, and worked OK for a while, then blew the fuse coming into the marina (we have to pass through a couple of bridges that are narrow and blind, so like to warn others coming out/in). Replaced again, only for a very feeble parp and another blown fuse. Any thoughts?
 
Intermittent short circuit. Check for abrasion, corrosion or melted/worn insulation on the cable. The horn should be a dedicated circuit, so its a case of tracing it from the DC fuse panel up to the horn switch and then on to the horn itself.

Very often it's the horn itself - the metal ones get corroded.

Check that you have the correct fuse rating.
 
Barry Jones said:
Intermittent short circuit. Check for abrasion, corrosion or melted/worn insulation on the cable. The horn should be a dedicated circuit, so its a case of tracing it from the DC fuse panel up to the horn switch and then on to the horn itself.

Very often it's the horn itself - the metal ones get corroded.

Check that you have the correct fuse rating.
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Thanks Barry. Fuse is 6A, and has worked fine for 3 years, so I believe OK. Will check the wiring at the horns end where it is more exposed. I have heard that horns can get clogged with Arakna and other ****. Any views?
 
I presume you are doing river and canal cruising in Stratford, so no salt involved.

It can often be just rust or a bad connection/stray wire strand.

Spiders and webs don't normally cause s/c's.

Do you know what size wire has been used ?
 
We are on the R Severn, so no salt as you rightly say. Again, have not changed the wiring, and this fault has just cropped up. No problems for the previous 3 years, so assume the wiring is OK.
 
Is it a twin horn ?

I normally fuse these slightly higher than 6A. Could be borderline.

Assuming that the cable used has sufficient c.s.a for safety, I would put a 10 Amp fuse in, but its wise to check the other things mentioned first.
 
If the horn is purely electro-mechanical, it works by means of an electromagnet pulling a diaphragm and simultaneously breaking a contact supplying current to the electromagnet coil, which then releases the diaphragm and contact, re-energising the coil, and so on, causing the parp. I guess the contacts are sticking closed, possibly because the diaphragm isn't free to move. The contacts are closed longer than they're supposed to be so the average current is far higher than normal, resulting in the blown fuses and weak parp.
 
rafiki_ said:
We are on the R Severn, so no salt as you rightly say. Again, have not changed the wiring, and this fault has just cropped up. No problems for the previous 3 years, so assume the wiring is OK.
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Bad assumption! wiring can, and oh too frequently does, develop faults - OK one day, buggered the next. - check for chaffed insulation etc or remove the horns and connect them to another battery via a 10A fuse and ammeter to see if the horns are at fault
 
They are twin horns. Not sure of the rating, but as posted earlier, have not had a problem previously for 3 years, so looking at what has changed? Will check for corrosion in the wiring as it emerges from the radar arch to the horns.
 
Have fun! electrical faults can be a real PITA to resolve - process of elimination.

I would check the horns first - seperate temporary wiring (with fuse) and if possible an ammeter to see if they are working and what current they draw. If they check out OK then have a look for chaffed cableing.
 
cliff said:
Have fun! electrical faults can be a real PITA to resolve - process of elimination.

I would check the horns first - seperate temporary wiring (with fuse) and if possible an ammeter to see if they are working and what current they draw. If they check out OK then have a look for chaffed cableing.
Click to expand...

Will do thanks. Culprit likely to be at the horns end as the wiring emerges from the arch.
 
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