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Troubleshooting Headlamp Out

Ken H.

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Well I have to tell this story (well I don't HAVE TO), if for no other reason than it's so darn funny...


Yesterday morning, hopped on the bike (R1200GS) and after starting it I got a front light out icon on the display. Sure enough, my low beam was out. So in that I have other aux. lights on the bike, off to work I went, with the intent of fixing it when I got home last night.


So I come home last night and after dinner go out to the garage to fix it. As you know, on the hexheads the headlamps don't come on until the bike actually starts...


So after fiddling around a bit to get the dust cover off the back of the headlamps' housing (the tabs have to line up just right) I get the bulb out and see that it is a H7. As luck would have it, I have a new one on the shelf.


Put it in, hook it up, and start the bike... Damn, still no low beam. So I shut the bike back down, take the bulb back out, get out my little handy-dandy 12 power supply and apply power directly to the bulb, and vo-la! Bulb lights, it's good.


Put it back in, fiddle with cleaning the socket contacts a bit (I know how fussy the CAN-bus module can be over high resistance), plug the bulb in, start the bike... Same story.


Shut the bike down again, get the voltage meter out, hook it up to the bulb's socket, start the bike... Again... No voltage. Damn! This starting to look complicated.


On the 12GS, like many other models, the whole headlamp module/unit has a connector going to it and the rest of the wiring to the lamps themselves is inside it. So I disconnect that connector, restart the bike and start testing for voltage there. On two of the pins I have voltage, I then reach over, flip on the high beam switch and now I have voltage on the other pin too. (They share a common ground.) Well, WHEW! At least it doesn't look like a controller or bike wiring issue... Must be something INSIDE of the headlamp assembly.


So to take that out, you have to disassemble some of the front of the GS (glad at the moment it's not a RT), including dismounting the instrument cluster from it, but in 30 minutes or so I have it out...


Now on the work bench, I start checking wire paths and resistance within the assembly with my trusty ohm meter. All along in the corner of my mind I'm remembering that burnt wires within the headlamp assembly have been a bit of an issue on, in particular the R1150RT, so I'm half expecting to find an open. But I'm not finding anything. So I decide to apply voltage from my 12v supply to the assembly. First I apply it to one set of pins – and one lamp lights. Then I change to applying it to the other set of pins, no light shines out anywhere! What the heck is going on??? The headlamp assembly and my mind are in total darkness.


The it dawns on me...















I had replaced the wrong dang bulb...

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Ken, that is a great tale, cheered me up no end on this wet October morning here in Nottingham. I have not got around to do anything like that.



YET lmao.gif

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Wanted to change the RH dip beam on the RT and, having done it twice, wondered why I kept getting duff bulbs. When I stopped chnging the main beam it made a world of difference. smile.gif

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My garage would have been filled with a lot of nasty sounds coming from me at about that point.
Well not saying there wasn't in mine too at the time. My only quandary was, who to yell at??? tongue.gifgrin.gif
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Well not saying there wasn't in mine too at the time. My only quandary was, who to yell at??? tongue.gifgrin.gif


Yelling at yourself is actually much more satisfying than yelling at others. Plus you never have to apologize.grin.gif

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You're scaring me man. I had one low beam bulb go out on my 05 RT yesterday and I replaced it last night. I know I changed the correct bulb but never physically started the bike to make sure it worked. Now I am afraid to go and start it.


Ok curiosity killed the cat right? I took the plunge. Just ran out to the garage and fired Ruby up. The replaced bulb works!!! That is no way to start a Monday morning Ken.

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