XR400: DC Conversion and wiring up a horn!

Hey Everyone!

Looking for someone who's got some electrical background and can give me some advice. I have only a tinkers level of electrical knowledge and I'm stumped.

I am setting up my XR400 as a DS and need to get the headlight and horn working. I decided to convert the bike to run DC power so I can potentially power a GPS down the line. The goal now is to Install a Headlight, Taillight, and Horn so I can get plated.

Here's what I've done so far with success:

Installed a Rectifier + Regulator from the stater leads to convert to DC.
Connected the R+R to a block that has many positive and negative leads.
Installed a TrailTech NiMH battery to the power block
Connected the power block's negative terminal back to the R+R's ground into the system.
Installed a headlight switch with Off/Low/Hi beams
Installed a Tail Light and Brake Light
Tested with a MultiMeter, The battery Draws 12.6 volts when the bike is off, and 14 volts when the bike is running at idle.

Everything thus far works just as expected.

Here's what doesn't work:
Installed the horn without relay. The power flows like this:
Power from positive lead > Wire to Horn Switch > Wire From Horn switch to Horn Positive Terminal > Wire from Horn Negative Terminal to Ground.

This doesn't work. When I press the horn button, it will honk for about 1/2 second then it stops. The entire system drops in voltage, down below 1 volt. Once I let go of the horn button, nothing changes. The entire system will remain less then 1 volt and the battery rapidly heats up. The only fix for this is to disconnect, then reconnect the battery. After reconnecting the battery, everything is fine (headlight, tailight etc.) until I press the horn button again then it drops again. Nothing will help the system to "recover" until I disconnect and reconnect the battery.

So I thought to myself, this is strange. Maybe this is because I was lazy and didn't use a relay. So I bought a different horn and relay. Tonight I installed the horn with a relay like this:
Switch Circuit: Wire from Positive lead to the switch > wire from switch to input on relay > relay wired to ground.
Horn Circuit: Wire from positive lead to relay > Wire from relay to horn > Wire from horn to ground.

I get out the multimeter and test. When I press the horn button I get 12.6 volts from the wire from the relay to the horn. At this point, I'm pretty excited and I hook up the horn! To my dismay, when I press the horn button I hear the audible click from the relay, but then the same symptoms. The whole systems drops in voltage and the battery begins to heat up. I can press the button multiple times after this, but no matter what the horn doesn't sound and the system will never get back to 12 volts until I disconnect, and reconnect the battery.

I am stumped - am I missing something simple here? Is the battery faulty? Do I need something else in my circuit?

Any help would be appreciated!

Thanks!
Jacob

It sounds like the horn is too much draw? You are shorting the battery somehow. The horn makes noise by make-and-break contact which vibrates the diaphragm, so maybe it's making and not braking. Try jumpers straight from battery to horn to see if that's the problem.
Most often, the horn takes power straight from the battery and the horn BUTTON grounds the horn. The horn is the largest resistance in the circuit, so the button (or the relay) are only taking the remainder of the current to ground. The horn winding is 'loaded' like an ignition coil.


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This worked out! I changed it up so the switch was just connecting the ground instead of supplying power to the horn!

Thanks for the tip!
Jacob

elgato said:

This worked out! I changed it up so the switch was just connecting the ground instead of supplying power to the horn!

Thanks for the tip!
Jacob

Click to expand...

Glad to help!