I can't get an aftermarket horn to work.

Nick V

Nick V

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Specifically, I can't get a single Stebel TM80 to work. :mad:

I cut the wires leading to the BMW two-pin plug that connects to the standard Bosch disc horn, and connected them directly to the terminals of the new horn.
The confusing part is that the horn works just fine if only the ignition is on. But when the engine is started and the horn button pushed, the horn activates for about half a second before the circuit is disabled. Pushing the button again yields no further result, and the bike logs fault code 800E84 (Horn, short circuit to ground), even though there is no such short circuit.

I did some deeper digging, and found that resistance on the standard disc horn is 2.5 Ohms. Resistance on the Stebel horn is 1.5 Ohms. I tried connecting a 1.5 Ohm 100W power resistor in series with the horn. The circuit is not disabled, but the resistor sucks enough current that although I can feel contacts within the Stebel working, the horn produces no sound.

Could this be the result of faulty/out-of-date motorcycle control software? To the best of my knowledge, the current motorcycle software version is Factory/Actual I-Level K001-13-02-500.

Has anyone else had this time-wasting fault? If so, how did you solve it?
 
The tm80 draws about 6 amps so the can bus will be shutting it down.
Use your original horn wires to switch a relay.
 
Doubt the horn is a purely resistive load. There will be some reactance in there too.
Short to ground......excessive load....same thing.
As has been suggested, the Canbus is shutting you down. Stick a relay in.
 
If the horn is mostly resistive at 1.5 Ohms then it draws 12/1.5 = 8A, if the supply is limited to 5A then there is the answer.

P.S. Measuring 1.5 Ohm accurately is not possible with a normal multimeter.
 
Hi Nick

As the other members suggested you can use a relay to allow the horn to draw power (high amps) directly from the battery and the relay coil (minimal amps) is powered by the original BMW horn wires. I recently used this method on my Denali horn and it work 100%.

Regards
 
Happy new year to everyone, and thanks for the input! :D
With today primarily being a social day, I can't work on the bike - but there are some loose ends I'm curious about.

Kenny Rodkiss said:
The tm80 draws about 6 amps so the can bus will be shutting it down.
Use your original horn wires to switch a relay.
Click to expand...

Sounds good, and I've already considered it. I wish I could find information on what the horn circuit current restriction actually is. The thing is, nothing so far explains why:
  • The Stebel horn works fine (and indefinitely) if the ignition switch is set to On, but the engine is not running, however:
  • When the engine is started and the horn button pushed, the horn activates for about half a second before the circuit is disabled and a fault code logged.

Why should the LINBUS / CANBUS only register an over-current / 'short to ground' condition while the engine is running, and not when it isn't?
It's obviously a function of some software protocol, but why should BMW have made that distinction? Or could it have been an oversight on the part of the programmer(s)?
 
When you turn the ignition on do you immediately test the horn? The bike turns on all circuits I guess for a few seconds (maybe doing a self diagnostic) then it cuts power to only the essentials, this is turned back on when the bike is started. This is evident that the driving lights are on but is turned off after a few seconds on battery only. Just a guess. Could be more to do with a SW protocol as you say. The output to the horn is controlled and theoretically can be logged if you have the SW schematics (to trace the output signal) and program to interact with the controller.

As the advice is use a relay. On my previous GSA I mounted the Stebel horn in tandem with the OE (no relay to switch) which gave it a nice twin horn sound. No problems then with current draw or CANBus.
 
Nick V said:
Happy new year to everyone, and thanks for the input! :D
With today primarily being a social day, I can't work on the bike - but there are some loose ends I'm curious about.



Sounds good, and I've already considered it. I wish I could find information on what the horn circuit current restriction actually is. The thing is, nothing so far explains why:
  • The Stebel horn works fine (and indefinitely) if the ignition switch is set to On, but the engine is not running, however:
  • When the engine is started and the horn button pushed, the horn activates for about half a second before the circuit is disabled and a fault code logged.

Why should the LINBUS / CANBUS only register an over-current / 'short to ground' condition while the engine is running, and not when it isn't?
It's obviously a function of some software protocol, but why should BMW have made that distinction? Or could it have been an oversight on the part of the programmer(s)?
Click to expand...

It doesn't matter the why and why not, use a relay and it will work.

However. The ZF unit which is the very fancy electronic fuse box (not CANbus which is just a data network) is set for both high and low power draw. High for a short and low for it isn't working. For high it cuts power to replicate a fuse function and resets when fault is cleared. Most items will show a fault on the dash although maybe not the horn.

As to why only when running, your on charging voltage which is higher there for the horn will have a higher amperage pull and it's possibly just enough to trip the limits.

Like it or loath it the systems as a whole have their advantages and disadvantages. The disadvantages are only to you. BMW has programed it this way to stop you pissing about with what they have created. Some of it are actually legal requirements like headlight conversions. The advantage to you in this instance is you didn't blow a fuse which you would have done and have to go buy more from halfords or wherever.
 
tanneman said:
The output to the horn is controlled and theoretically can be logged if you have the SW schematics (to trace the output signal) and program to interact with the controller.
Click to expand...

The GS-911 actually has a facility that allows you to log any parameter you want, then display it as a value-vs.-time graph. :D
Useful to know if you have a mysterious fault that's power-dependent, but...

tanneman said:
As the advice is use a relay.
Click to expand...

...Since I'm going this route anyway, I won't need it for now. :)

If you want a Stebel Nautilus over here, you have to import it yourself, get it through an international retailer, or whatever. But the other day, I was in a parts store, and saw a Chinese copy of what was obviously a Nautilus. I can't remember the quoted sound pressure output, but I have a hunch it was around the 117 dB mark. If that's correct, that would be double the effective volume of something producing 114 dB.

Oh, and that's the other thing... has anyone here managed to install a Nautilus (or equivalent) on an LC GS? If so, where on Earth did they put it? It's not small. :confused:
 
Nick V said:
Oh, and that's the other thing... has anyone here managed to install a Nautilus (or equivalent) on an LC GS? If so, where on Earth did they put it? It's not small. :confused:
Click to expand...

Nick, try ADVrider. I'm sure the Mercins have found a place for it.
 
Hi

I see NN do an aftermarket horn fitting kit for the water-watercooled GS.
 
I made a bracket up and mounted one on each crash bar, make sure they point towards the rear otherwise they will fill up with water if it rains hard while you are riding
 
Nick V said:
Why should the LINBUS / CANBUS only register an over-current / 'short to ground' condition while the engine is running, and not when it isn't?
It's obviously a function of some software protocol, but why should BMW have made that distinction? Or could it have been an oversight on the part of the programmer(s)?
Click to expand...

Perhaps when the engine is running the battery voltage is slightly higher and therefore the current is greater and sufficient to trip the overload event.
 
All sorted. I'll try and post pics I took of the installation when I can, but for now, a brief description will have to suffice.
I would class the horn relay installation as 'very easy' - but one big factor reduced time and stress: I already had a fused 12V+ supply leading from battery + up over the right-hand radiator to power a spotlight installation.
  1. The circuit takes power directly from battery +.
  2. Battery + leads to a waterproof 'compact' blade-type fuse holder. I mounted this so that in order to get to it, the only thing that needs removing is the small RHS black plastic panel under the fuel tank.
  3. The wiring runs from the fuse holder up in front of the fuel tank and over the right-hand radiator, to the point where the RHS snorkel enters the airbox.
  4. At this point, the fused 12V+ supply is split. The horn power enters the relay (the horn and spotlight relays are both mounted to the top front radiator mounting).
  5. Horn power travels from relay output terminal to horn (mounted on original BMW laminated bracket).
  6. Horn power travels from horn to earth terminal (at top rear radiator mounting).
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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