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Fiamm horn/relay question.

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wa1nca
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Re: Fiamm horn/relay question.

Post by wa1nca »

IMG_20240402_115536_MP.jpg
Ok
To add a relay to support 2 or more horns
Remove 15 anf HO wires from the horn
Connect the coil on a relay to 15 and HO
Add a jumper from 15 to center contact of relay,then a wire from contact of relay to feed power to the 2 horns in parallel and ground as shown

Now when the horn button is depressed the relay closes contacts and send power to both horns

Not sure were you relay is located but should give a better idea how to connect the relay wires as you said it did work earlier
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

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srankin
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Re: Fiamm horn/relay question.

Post by srankin »

Tommy, do you have a better picture of the wiring diagram you are referring to? Or what is the wiring diagram you have a picture of for what year and model bike?

So, in your configuration, where is the higher current draw power coming from?

I can see where you are getting the low current trigger power from.

How does your diagram compare to the relay he has on hand? St.
Owner of a 84, R80RT and 78, R100RS

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wa1nca
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Re: Fiamm horn/relay question.

Post by wa1nca »

R90s/6
R90S+Wiring+Diagram.pdf
(304.82 KiB) Downloaded 13 times
Power from headlight terminal board #15 8 amp fuse to #86 stater relay then to #15 horn

I don't know what he has for a relay or where it was located (headlight shell or near horn)
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

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wa1nca
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Re: Fiamm horn/relay question.

Post by wa1nca »

I just read this thread from the beginning !!
What a mess
Does a additional horn button gets added so the relay get power to energize the relay to power the dual horns with a larger red feed wire and still have the original horn setup
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

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RideSolo
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Re: Fiamm horn/relay question.

Post by RideSolo »

Many, many thanks to all who jumped in. I'm going to go w/ the easy fix. The relay goes away, I'll pick the horn, of the two, that sounds better, and connect it to the + and - wires from the harness. Easy, done, and no worries. It came to me w/ two horns and a relay but I have no idea how they made it work and I'm not married to that lash-up. As long as I push the button and it goes "BEEP" that's all I really care about. If what I've got doesn't seem loud enough I'll find one that is. Most single horns that I've looked at seem to be rated at 3 or 3.5 amp. I'll bet those Fiamms are so old they may draw more than that... no wonder I blew the fuse.

The old girl is 50 years old and has been sitting for the last 35 years. The guy I bought it from was absolutely no mechanic by his own admission so everything done to it was done by the original owner. He was an older German gentleman in the Cincinnati area who meticulously took it to the dealer every 5,000 miles like clockwork but as I've gone through everything it's seemed like that was the limit of his meticulousness; I've found very little attention to detail and care. That's ok, it's now got a good home w/ me and I'm trying to move it into being a lovingly maintained and quiet "old man's bike" with new OEM replacement parts as necessary and period touches like the Wixom panniers, R90S fairing, Brown side stand, and Lester wheels. But at the same time I want to actually USE it so I've done a R90X front brake conversion, bar-end mirrors, and switched to stainless fasteners. I expect it'll serve me well and make me happy for many years.
'75 BMW R90/6 "Rocinante"
Cory E.
Bucyrus, Ohio
Retired USAF

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srankin
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Re: Fiamm horn/relay question.

Post by srankin »

Oh man, I am so sorry to make this into such a big thing.

Yeah the single horn will draw 3 or 4 amps, less than the fuse cut out. Maybe some other larger horn may draw the same or less, a single horn of the dual horn system (high tone horn paired with a low toned) will draw under 8 amps.

Wa1nca may have hit the nail on the head as to where the mystery high current power lead to supply the horns came from. Off the starter relay. Check on the starter relay under the gas tank and look to see if perhaps the red wire at pin 30 has been tapped into. This would mean a short wire from that relay to the mystery relay. And the mystery relay could have been mounted near the starter relay under the gas tank. So no long wire running to the battery.

Then the trigger current would be the green/white or in his diagram green wire and brown wire at the horn.

So, LOL, after all the confusion, if you still want to hook up dual horns, that would be the way to do it.
Owner of a 84, R80RT and 78, R100RS

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Re: Fiamm horn/relay question.

Post by srankin »

I love restoring older BMW bikes, once sorted they are just great. St.
Owner of a 84, R80RT and 78, R100RS

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Re: Fiamm horn/relay question.

Post by RideSolo »

I wanted to close out this issue as best I could. By way of explanation, I've been on numerous different boards like this for years for various different vehicles/interests and have gained insight and knowledge from following threads on various subjects/problems. It's always been helpful to me when an issue had been resolved and documented. In that spirit I thought I'd post the resolution so that perhaps someone in the future isn't left w/ a cliffhanger.

The single horn works however it wasn't w/o problems and pitfalls. I couldn't get my little brain to wrap itself around how in the world they had made the whole Fiamm horn w/ relay lashup work in the past. It shouldn't have! Many chimed in here and attempted to assist and I really appreciate their inputs... some I followed and understood and others I had to just say, "Huh?" (Note the "little brain" comment above, I try to work w/ what I was given!). Anyway, I thought I had it all figured out and went to work connecting and testing: Yep, all good! So I then did up the wiring I need and tested again: Yup, all good! The next step was to heat shrink and wire wrap everything and test again: Yup, all good! Then I mounted the horn, tested: Turn on the key and "BEEEEP!" Obviously a dead short but not the fuse-blowing kind. I unhooked the battery, turned off the lights, locked the shop, and went in the house. After a couple minutes thinking I realized what was going on; a + wire and a - wire and a grounded horn creates a dead short when the key switch is turned on. The next morning I went out and took the horn off the bike and, sure enough, all worked as it should. I used some plastic washers to insulate the horn from the frame and we're now good, beeping good.

Back to the relay: it's housed in a plastic case and was mounted to the frame with a bolt through a plastic tab w/ a hole in it so when mounted, the relay wasn't grounded. There was no direct power wire connected to the relay to power it's coil. I think they somehow used the + wire from the horn button to power the relay as well as the horn. Someday if I'm really bored I may dig the thing out and mess with it again but for now I've achieved what I needed; an operative hooter, alles gut und fertig.
'75 BMW R90/6 "Rocinante"
Cory E.
Bucyrus, Ohio
Retired USAF

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srankin
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Re: Fiamm horn/relay question.

Post by srankin »

So am I reading correctly, you installed one horn or two?
I really don't think you need a relay for just a single horn even a fiamm current draw from a single horn should not be more than 8 amps. Less than the fuse blow point. Are there specifications for the horn's power supply?

I don't want to mess with your head much more than I have but, there is no + horn button wire. The horn button is a ground switch.

The + for this circuit is the Green/black wire. So power flows from the green/black wire through the horn, and is grounded to complete the circuit when the horn button is pushed.

There maybe current at the horn button, but is sourced from the horn, take out the horn and use only the two wires for the horn button Brown/white and brown, you will get no power.

There, LOL, I just can't be a know it all, sorry. St.
Owner of a 84, R80RT and 78, R100RS

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Re: Fiamm horn/relay question.

Post by RideSolo »

srankin wrote:
Mon Apr 08, 2024 11:27 am
So am I reading correctly, you installed one horn or two?

I don't want to mess with your head much more than I have but, there is no + horn button wire. The horn button is a ground switch.

The + for this circuit is the Green/black wire. So power flows from the green/black wire through the horn, and is grounded to complete the circuit when the horn button is pushed.

There maybe current at the horn button, but is sourced from the horn, take out the horn and use only the two wires for the horn button Brown/white and brown, you will get no power.

There, LOL, I just can't be a know it all, sorry. St.
No know it all here either, for sure, just an old retired USAF NCO office administrator who's happily trying to keep learning and growing... hopefully not just growing around the waist!

One horn. I applied power to each of the two and picked the clearest, loudest, and most noticeable of the two.

My phraisology. :-) I was referring to the green/black as the + wire. When I attached my volt/ohm meter, + to the green/black and - to the brown/white, the meter would show a bit above 12vdc when I pressed the horn button. That's where I was getting my context for the + and - wires. In my old world of Japanese motorcycles there's usually one "horn wire" and the circuit is completed by energizing that wire via the switch and said energy flows through the horn and completed the circuit by grounding on the frame. I'm learning... I hope.
'75 BMW R90/6 "Rocinante"
Cory E.
Bucyrus, Ohio
Retired USAF

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