When i switch to bright lights the lamp goes out. Does that sound like wireing or is the bulb out? I thought the low beam would stay on even when you swithch to high beam.

 

Start with your bulb. Always work the problem from the simplest solution to the more complex. If I'm not mistaken, these bulbs have 2 filiments in them. Get a voltmeter set for continuity or resistance, and look for a open reading across the terminals on the bulb. Or you might be able to see the faulty element upon inspection.

 

By brother-in-law just had this exact issue on his 2003 right after:

A: Washing his bike and;
B: swapping out handlebars

We think there was some water creating a short or something, because the next day, the issue was resolved.

Is the bulb being burnt out? Or is the 15amp fuse popping?

 

No, they are separate bulb filaments, and normal operation is one or the other.
Replace the bulb.

 

Most likely a bad bulb

 

Doesn't the switch only direct current to the highbeam? I mean the lowbeam is always on so when you engage the high it connects the power to the highbeam, thus the low stays on with it. I agree that you should start with the bulb, but something tells me it is the switch or switch wires.

 

No, unlike a regular light switch on the wall in your house which is an ON/OFF switch, the bike's switch has no OFF position, it is an ON/ON switch. It turns on either the low-beam or the high-bream.

 

Headlights on sporty's are dual filament, odds are it does not give power to the low when the high is on as is typical with a dual filament bulb. Just because the low is always on doesn't mean it will be on with the high, by flipping the switch you're changing the the circuit to complete the high instead of the low.

Go with the bulb, they don't last forever.

 

I have the electrical diagnostic manual for 2011 Sportsters. The wiring diagram shows the high beam connected to the 3 terminal plug utilizing the black wire (terminal 4 common or ground) and the white wire(terminal 2). Test the bulb first with an ohmmeter (continuity) as per xwhyz1959's good advice. If bulb is good, test the wiring by connecting a DC voltmeter across the white and black wires and switch the headlamp switch to Hi beam. You should read 12 volts DC. Just to make sure you are on the correct wires, connect the voltmeter to the black and yellow wires and switch the headlamp switch to Lo beam and you should read 12 volts DC. The two elements of the headlamp are separate and should not be on at the same time. If you do not read 12 volts DC at the selected terminal, you may have a bad Hi beam wire.
Your wire colors may be different than the 2011 Sportsters but the testing method should be similar. If you don't have a voltmeter you can use a spare turn signal or brake bulb with two wires soldered to it's terminals as a test light. Just connect the test light across the head lamp plug terminals and operate the switch. If it glows in the correct Hi beam position, your wiring and switch is good. Most likely a bad bulb.

 

If you really want to test the bulb, just look at it. You can see when a filament burns out. It will be broken, a section may be missing, the bulb could have a smokey discoloration.

Seriously people, it's just a light bulb, not rocket science.