Horn Change on K100 & R1100

Paul_F · Jan 5, 2020

i picked up two FIAMM Freeway Blaster horns to replace each of the horns on my '87 K100 and '98 R1100. The max amp draw is 6 per horn.

Is it possible to use the existing horn wiring without having to install an additional relay? Six amps seems low and I am guessing the original horns must have some protection.

Having no electrical expertise, I hope that someone can advise me as to whether or not relays are necessary.

98lee · Jan 5, 2020

Paul,

The stock horns are already driven through a relay. They are protected by a 15 amp fuse in the bottom location of your fuse block.

However, that fuse is also the fuse for your fan. I don't offhand know what the current draw for your fan is, but it is probably more than 3 amps.

It is NOT permitted to increase the fuse size on these bikes as the limiting factor is the wire size. If you increase the fuse size, you could melt the wires, which is the what the fuse is there to protect.

You could try it by getting several 15 amp fuses (you should always carry several spare 7.5 and 15 amp fuses anyway), get the bike warm so the fan kicks in (letting the bike idle for 10-15minutes with no other airflow to the radiator should do it), and blast away with your horns for 30 seconds or so (you might want to tape some rags around the horns so your neighbors don't call the police). Keep an eye on your temp light. If the light comes on before the fan starts, you either have a blown fan fuse (#7 at bottom) or your fan is shot. If you have a gauge, the fan should come on before 210. I don't have the exact temp in front of me right now. Just don't overheat the bike for too long. You can cool it down quick by riding it or putting a big fan to the radiator after your test.

Remmember to ALWAYS carry several of each size spare fuses.

:dance

Paul_F · Jan 5, 2020

98lee said:
Paul,

The stock horns are already driven through a relay. They are protected by a 15 amp fuse in the bottom location of your fuse block.

However, that fuse is also the fuse for your fan. I don't offhand know what the current draw for your fan is, but it is probably more than 3 amps.

It is NOT permitted to increase the fuse size on these bikes as the limiting factor is the wire size. If you increase the fuse size, you could melt the wires, which is the what the fuse is there to protect.

You could try it by getting several 15 amp fuses (you should always carry several spare 7.5 and 15 amp fuses anyway), get the bike warm so the fan kicks in (letting the bike idle for 10-15minutes with no other airflow to the radiator should do it), and blast away with your horns for 30 seconds or so (you might want to tape some rags around the horns so your neighbors don't call the police). Keep an eye on your temp light. If the light comes on before the fan starts, you either have a blown fan fuse (#7 at bottom) or your fan is shot. If you have a gauge, the fan should come on before 210. I don't have the exact temp in front of me right now. Just don't overheat the bike for too long. You can cool it down quick by riding it or putting a big fan to the radiator after your test.

Remmember to ALWAYS carry several of each size spare fuses.

Thank you Lee.
The installation and testing will have to wait until the snow melts. I always have extra fuses with me for both bikes. Fortunately, only once was one needed. :dance

Horn Change on K100 & R1100

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