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Old 01-19-2013, 10:41 PM   #177
2 Many Motersikles
RocketMoto's Avatar
Joined: Jun 2008
Location: New Haamsha, USA
Oddometer: 956
Originally Posted by COMESEEGO View Post
1. If so, use the PDM60 output1 directly with a new horn and connect the gray (no, I meant blue) PDM trigger wire to your BMW horn button (I assume it also switches like on the R1150RT to ground). Clean setup -> Extra relay gone
With regards to the BMW horns, the factory horn connector always has ground present on the BROWN wire and +12 volts is switched to the horn on whatever the other color wire is. You definitely don't want to connect the PDM60 BLUE wire to trigger from the BMW horn lead.
The blue wire is a high impedance input intended for a GROUND trigger. Ground it, and the associated circuit(s) will output 12 volts. BMW horns have ground present all the time, and 12 volts is switched to the horn, so to get ground from the horn circuit, a relay is needed. Make sense?

Hello Adam,
Maybe the drawing will show what I mean. (The BMW horn circuit is from a 2001up BMW R1150RT wiring diagram) Without pressing the horn button the connection point of the blue PDM wire at the BMW Horn Relay is high (+12V) but when the horn button is pressed the connection point is pulled to ground. Shouldn't this work with an additional horn connected to the PDM60 output #1?
Regards, Joe

Aha! Got it. Picture's worth 10,000 words...

That'll work fine. So long as you connect the blue PDM60 wire to the ground side of the relay coil that is applied by the switch, what you want to do will work.
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