Light and radiator fans not working

[Vmax1700@]

Hi Vmax fans,
I wonder if you can solve this mistery:
I replaced the standard horn with a better after market horn.
After that, I noticed my radiator fans did not work anymore. I tested some things with the two relays (fans and light) under the rear fender, and then notice my headlight wasn’t working. I’m not sure if I caused that by checking the relais, or if it stopped working together with the fans. When I short circuited / bridged the fan wire in the relay socket; the fans still didn’t work.
Then I found out that the original horn is used as a ground for the fans. I connected the ground wire of the removed original horn to the chassis, short cutted / bridged the relais again, and the fans work.
BUT: the fans and headlight still do not work via the relay as they should. Only when I shortcut/bridge the relays.
So a long story short: fans and headlight do not work. Relays get no power.
Any advise to solve this mistery is highly appreciated! Thanks!

 

[02GF74]

It sounds like something is f***ed

Then I found out that the original horn is used as a ground for the fans.

Who told you that?

Car and motorcycle horns use the sane design since year dot.

I searched vmax 1700 horn, see below, and it has two terminals. These power an electromagnet to vibrate a diaphragm, one is power, one is ground.
I don't see how it us possible for fans to be grounded via the horn, the fans will have their own ground wire, that yes, will ultimately connect to same ground as the ground wire for the horn. Maybe I'm arguing a technicality.

Do you have wiring diagram, and can post it?

 

[Parminio]

I replaced the standard horn with a better after market horn.
After that, I noticed my radiator fans did not work anymore.

So, you fixed what wasn't broken and now it's broken.

What's the old saying?

 

[MaxMidnight]

When you replaced it did you just unplug the old unit and plug the new one in or did you perform surgery elsewhere?

If it was the former and assuming the bike doesn't use a CAN bus system then I can't see why a strait swap would cause the issue you describe.

The only common link that I can see between the horn, fan and headlight relays is that they all go to earth. The horn and fan do this directly and the headlight via the headlamp switch and light assy.
Re the fan, is it both motors that aren't working or just one?

If you put the old horn back in does the fan and lights work OK?

It sounds like something is f***ed

Car and motorcycle horns use the sane design since year dot.

I searched vmax 1700 horn, see below, and it has two terminals. These power an electromagnet to vibrate a diaphragm, one is power, one is ground.
I don't see how it us possible for fans to be grounded via the horn, the fans will have their own ground wire, that yes, will ultimately connect to same ground as the ground wire for the horn. Maybe I'm arguing a technicality.

Do you have wiring diagram, and can post it?

Agreed, there is a power feed in from the switch and the other terminal goes to ground.

Have attached the wiring diagram.

 

[Vmax1700@]

When you replaced it did you just unplug the old unit and plug the new one in or did you perform surgery elsewhere?

If it was the former and assuming the bike doesn't use a CAN bus system then I can't see why a strait swap would cause the issue you describe.

The only common link that I can see between the horn, fan and headlight relays is that they all go to earth. The horn and fan do this directly and the headlight via the headlamp switch and light assy.
Re the fan, is it both motors that aren't working or just one?

If you put the old horn back in does the fan and lights work OK?



Agreed, there is a power feed in from the switch and the other terminal goes to ground.

Have attached the wiring diagram.

Hi,
Thanks for your efforts
I used the same cabling as the original horn. So lateron I discovered the ground of the fans was somewhere disconnected and needed to be reconnected. During that “discovery”, i think the relays (light and fans) under the rear fender got damaged due to wrong cabling of an Optimate charger (the cable (original!) clamps provided with the charger were wrongly connected: + and -).
Now I ordered new relays, and still the problem remains; no light, no fans. When I shortwire the relays (the switching contacts), light and fans work. I start to assume the ECU is damaged. Any way I can test that?
Thanks in advance!