hi al lwhile out riding in the dark last night my headlamp started going of then coming back on without touching the switch the bike still ran ok was just very unnerving as the traffic out of the city was quite heavy even late at night

i have notice that it does it this evening even when the bike is stationary and nothing moving am i right in thinking that hds have themal fuses and one could be on its way out bike is a 91 flstf

any help much apreciated

Dan

 

a fuse is either intact or blown its not a case of on its way out. just check your conections something has probabley made its way loose.
check the - you may have to take it off and clean it then re-fit it a little corrosion may have over time made a good conection a bad one.

 

agreed...if it were a fuse they would shut off completely. My guess would be bad wirring or connectors. Hopefully it isn't the wirring harness under the tank. good luck though

 

Agree it's probably a loose connection somewhere; check the headlamp bucket where the wiring is connected to make sure they are all tight.

 

Check it by running it both on low beam and high beam. If its only one then the headlight itself could have a broken filament but not likely. If it is going out on both high and low, it has to be a connection. Make sure the head light fixture is tight to the bike framework and as said on another post, check all the connections inside the fixture.

Let us know what you find!

 

Had the same issue on my fatty it was a loose connection a little solder shrink tube and wala no more black outs

 

i had the same issue on my bike.
found out to be a loose connection . i replaced the h4 connector that goes to the connection on the head light and solved the problem

 

Check to see if you have fuses or breakers( auto resets ), if you have breakers you could be tripping them with an intermittent short .
my nephew's bike had a wire with cracked insulation resting against the frame, the headlight would slowly flash on and off because the breaker kept trying to reset.

 

high beam and low beam run off different wires. You can get your high beams to work even if low beam doesn't. As i found this out when i rewired my bike. I had high but not low. Also if it is a filament issue it works just as a fuse would either it blown or not blown. I'm sure your issues are with your wirring/connection/harness. Good Luck

 

Most two filament bulbs work off a common ground return. If both high and low are acting up the possibility of a loose ground return is quite likely. Filaments are not fuses. Sometimes they will connect back together when you hit a bump in the road, I admit it is not likely but it does happen. Sorry to disagree but I have been working electronics and electricity for 40 years.