2007 R1200GS horn functions in the ZFE module

[dritch1970]

Greetings,
I have a diagnostic question about troubleshooting the ZFE module which controls the horn circuit. The bike has an aftermarket horn which is wired correctly through a pilot duty relay. This worked intermittently when i purchased the bike and has now quit.

I ordered the GS911 from Beemershop and it should arrive tomorrow.
My question is this:
I assume the horn button is a digital input (dry contact) to the ZFE. The module in turn must fire an internal relay to provide 12 VDC to the horn. I am not receiving the 12 VDC to the horn wire.
Does the GS911 have the details to verify the horn button is made-can you see inputs for this?
I do see you can test outputs-I guess I could try the horn test output on that note.
What are the conditions to make the horn blow?
Just the input from the button? I also assume there is some kind of current limiting feature on the output.
Thanks

[Beemerboy]

Hello,

What I did with a pair of Stebel horns, that I mounted on my GS (2010)
I took the wires off the standard horn, and with that voltage I make a relay engage. (contacts 85 and 86 )
Then I got a wire with a fuse and connected it to the + of the battery and the other side to contact switch of the relais (contact 30 )
Other contact ( 87 ) to the + of the new horn.. the other contact of the horn to the bikes massa -

The down side is that this configuration triggers a fault, as the ZFE module sees the (minimal) current that the relais is drawing as a
'break'in the horn wireing. But that fault doesn't shows up on the dashbord. You see it only when you do a fault readout with the GS911.
I can live with that.

[dritch1970]

My horn wiring is exactly as you describe. Upon using the GS911 it tells me the fault code is a Short Circuit on the horn output. So I assume this is either the wiring between the ZFE module and the relay or the relay itself.
I will do some more testing to make sure.
Thanks!

[Beemerboy]

Hi..

First thing I would try is to take the wireing that in your new situation goes to your relay at take them of the contacts,
so it hangs loose. Then see with your GS911 if now the fault code is: wireing horn loose (or something like that)

Its possible that your relay has a so called damper-diode over the spool ( I don't know the enlisch word for it sorry)
and if that is so, than its important that you put the wire that comes from your ZFE unit on the right contact of your relay.
if you put them on the wrong contacts the diode let the current trhough and the ZFE unit sees that as a short circuit.

[Beemerboy]

I quickly looked it up for you and this is what I found:

Using a relay with a diode across the coil can prevent this damage by absorbing the high voltage spikes
and dissipating them within the coil/diode circuit (this is known as a blocking or quenching diode).
The diode will always be installed in the relay with the stripe on the diode body facing towards terminal 86 (reverse biased)
and it is important that +12V is connected this terminal,
NOT 85 (as per the DIN standard) or the diode could be damaged.

[dritch1970]

As it turns out the control wire for the relay was pinched under the gas tank.
 I checked ohms to ground and sure enough a dead short.
I replaced that wire and routed everything correctly and all is well.
Except now the fault is Open which I too can live with.

[Beemerboy]

  me too