Who knows how many AMPS ?

[Cucciolo]

Anyone knows how many AMPS has the fuse that is connected to the horn? AND what else is connected to this fuse along with the Horn? in example, is the head light and the horn and the blinkers connected to the same fuse? Trying to find out how many amps are there to spare on a replacement to the stock horn. Any help will be appreciated!
Thanks

[jdubbs32584]

Hon, try posting this up in the Tech section. Alot of technical questions can be answered there.

[Ohmic]

What year of your bike?

[Cucciolo]

What year of your bike?

S4R 2005 ...

[Howie]

10 A, stop light, horn, speed sensor

[Cucciolo]

10 A, stop light, horn, speed sensor

Would you happen to know how many amps the Speed sensor and the Stop light each draw?

[Ohmic]

julianista,

According to your owner's manual. The 05' S4R has a 10A fuse for the Horn, Stop Light & Hall Sensor located in Section 7-15 on the fuse block.

Horn: No wattage information given in User Manual My Monsters are in the shop. I looked at the one on my 02' MH900 and its horn has a 48W rating stamped on it. Thus it will sink 4Amps @ 12V. Assume similar part on your Monster. But it won't hurt to double check the horn on your bike.

Stop Light: With the stock 1157 bulb. Said fuse will source  1.75 Amps to the 21W filament of the stock bulb. The 5W filament(running light) is sourced from different fuse.

Hall Sensors: Again no power rating. This is your speed sensor. I've worked with many transducers of this nature. I can't see it using more then a few 0.001 Amps. In the big scheme of things when compared to the Horn and Light. Its noise. Ignore.

So.... you have a 10amps fuse - (4 Amps + 1.75 Amps) = ~ 4.25 Amps tops maybe slightly less coz of Hall senors.  Good practice is to stay below of 80% of max rating of fuse. This is a buffer for ambient temperature swing. Bottomline... new horn? Remove stock horn and keep the new horn to around ~75W or lower. Else increase Fuse.

[Cucciolo]

Ohmic,

Very helpful information. Thank you very much!

I did look in the manual, but couldn't find the amps on the stop light nor that there was a speed sensor. The new horn I am installing will draw 6amps.. so if I had the stop light and the horn plus sensor all working at the same time it will draw a total of 7.75amps.. not adding anything for the sensor. I would still be under the 80 percent you mentioned. Therefore I would not need a relay for the horn. Am I correct on this statement?
Also, the manual states under WARNING. to never use a fuse with a rating other than specified otherwise it may result in in failure or even fire! So if the Sensor really drew a few amps, then would I have to install the relay?
Thanks again!

[Ohmic]

The sensors draws milli-Amps. 1/1000's of an Amp.
Your calculated worst case scenario is 7.75Amps. But in reality it is under this number if measured. Manufactures publish specs that is always a little more conservative to save their butt. So we have to use what is published in the datasheet also to save our butt.

I'm betting my 48W horn on my MH in reality draws less then the calculated 4 Amps at 12V. Plus... the horn load is not a constant load. It is turned ON what?.... 0.00001% of your ride time? So your 10Amp fuse is not constantly stressed.

You're cool with the 10Amps fuse. No need to clutter up your Monster with a by-pass relay. You can always save an Amp or more by going with LEDs for the stop light.

Also, the manual states under WARNING. to never use a fuse with a rating other than specified otherwise it may result in in failure or even fire! So if the Sensor really drew a few amps, then would I have to install the relay?
Thanks again!

Very true. However note. People generally believe that fuses are in place to protect the load. Not true. It is there to protect the wiring harness upstream WHEN something goes wrong with a load. By that time it is too late for the load. Something HAS already gone wrong.  So if the wiring can handle it. And your load has increased. I don't see why the fuse can't be increased slightly so it don't trip with the additional load.(bigger horn in your case).

[Cucciolo]

Great info man!! Thank you!

That scenario would not be atypical.. if you are braking and using the horn at the same time because soccer mom is about to run you over..

even if I reach 10 amps of load by running everything simultaneously, will the fuse blow immediately or it can hold the load for a few secs?

oh.. the stock horn is 4amps. I removed it to check it out for you!

[Ohmic]

even if I reach 10 amps of load by running everything simultaneously, will the fuse blow immediately or it can hold the load for a few secs?

You won't reach 10 Amps.  BUT if you did. I'm not sure if the 10Amps fuse is a Slow Blow delay fuse. To be honest I've never read its datasheet.

oh.. the stock horn is 4amps. I removed it to check it out for you!

Same. Yeah. Makes sense for Ducati to use same from a manufacturing standpoint. I too just removed the 48W unit off the MH and placed on the lab bench. Applied 12V with current probe in series. It was  L O U D  indoors  . And the gf was like  .  Anyway... it drew only 3.1 Amps as I had suspected. Not 4Amps per specs. So you see... you have room to play and some.

[ducpainter]

The sensors draws milli-Amps. 1/1000's of an Amp.
Your calculated worst case scenario is 7.75Amps. But in reality it is under this number if measured. Manufactures publish specs that is always a little more conservative to save their butt. So we have to use what is published in the datasheet also to save our butt.

I'm betting my 48W horn on my MH in reality draws less then the calculated 4 Amps at 12V. Plus... the horn load is not a constant load. It is turned ON what?.... 0.00001% of your ride time? So your 10Amp fuse is not constantly stressed.

You're cool with the 10Amps fuse. No need to clutter up your Monster with a by-pass relay. You can always save an Amp or more by going with LEDs for the stop light.

Very true. However note. People generally believe that fuses are in place to protect the load. Not true. It is there to protect the wiring harness upstream WHEN something goes wrong with a load. By that time it is too late for the load. Something HAS already gone wrong.  So if the wiring can handle it. And your load has increased. I don't see why the fuse can't be increased slightly so it don't trip with the additional load.(bigger horn in your case).

Ducati wiring harnesses are not constructed with accessory electrical equipment in mind. Most of the wire is 16 or 18 gauge. It will handle more than ten amps...but not much.

I'd go with a relay before changing fuse sizes.

[Cucciolo]

thank you for the great info!

I will install the 6amp horn without a relay then. I wanted to avoid the relay installation at all cost.. so thanks for the help!!!