2008 Fatboy Headlamp wiring problems, stock bike, 20,000 miles. The low beam was not working but the high beam was. Normally a new bulb would only last me a year, so I am on my third bulb. Replaced the bulb and was still having problems with no low beam. Noticed that the three prong female socket, which the bulb plugs into, had overheated at some point, as there were small bubbles of plastic on the socket. The new low beam would light but only when the socket and plug were manipulated. Since Harley does not make a replacement socket pre-wired, I was able to find an automotive female socket pre-wired for three wires, which worked with the new bulb. I simply crimped new connectors onto the old wires and then connected them to the proper three wires on the pre-wired socket, basically same wiring as before. The lamp now works correctly but the high beam indicator light on top of the fuel tank console is lit continuously. The wires on the pre-wired automotive socket are #12 wire, while the original wiring is #14, I believe.

 

Usually a bulb that is too high of a wattage will cause the connector to melt. I have also found the ground inside the headlight bucket is weak and will make a new one when I have issues. I put the new ground on the tank bolt.

Drew

 

If you're buying a new bulb every year, you may as well get the LED bulb now. It'll run a lot cooler and should last you a lot longer. You really shouldn't be replacing that bulb nearly that much.

 

You should not have to replace your bulb every year. Something is wrong. I have been running the same bulb for 3 years without issue and I ride nearly everyday with the thing on bright!

Drew

 

First... like Dr V-Twin said... GROUND. The bucket ground is another HD engineering masterpiece. Run a good ground.

Second... buy a quality "ceramic" plug instead of plastic... then you can run any size bulb that you want. In fact I have my light wired to run high and low beam at the same time... melted the plastic plug, but have been running a ceramic plug now for 3 years with no problems.

 

I tend to believe crappy ground or even dirty connectors also. My son's headlamp went out, and the high beam indicator stayed on, but no high and low out of the lamp. Took the lens off, and yes the connector was fused to the bulb terminals, but not too major beyond reuse. The ground is riveted to the bucket, and I could twist it left and right, which tells me the arc caused the heat (not the bulb itself). I also noticed that the socket was previously replaced before, and the leads were soldered, so no issues there. For a quick fix, I crimped the rivet, cleaned the terminals with a small file to get to bare metal, and put dielectric grease in the socket. So far it did not go out again. The HB indicator being on tells me to check your ground and connections again.

I used to go through melted sockets and burning out bulbs on my GM, but since I cleaned the terminals and added dielectric grease, on 3 years now with no further issues with the same half melted sockets. Give that a try.