Popping 'headlight 'fuses.

I have a modulator on my bike. They have run great for 2 years. Two times in two weeks I popped 2 fuses. I normally run with it on. I remember I am running the H4's. My questions is two fold. One, can the bulbs draw more as they age? Two, is 8there an led replacment yet? Alsp can I go to a 25amp fuse?

STmark1300 said:

I have a modulator on my bike. They have run great for 2 years. Two times in two weeks I popped 2 fuses. I normally run with it on. I remember I am running the H4's. My questions is two fold. One, can the bulbs draw more as they age? Two, is 8there an led replacment yet? Alsp can I go to a 25amp fuse?

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Dunno the answer to the bulb aging question, but can you easily disconnect the modulator and see if the fuse problem goes away? If it goes away then the problem is in the modulator, if it doesn't then perhaps you have some other wiring issue like an intermittent ground problem. Don't change the rating on the fuse, its there to protect the wiring, which is much more of a pain to replace than the fuses.

I am not sure how to isolate it. Does Taking out a bulb tell you anything?

STmark1300 said:

Does Taking out a bulb tell you anything?

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not really, but I would connect it to the battery directly and take a current measurement as a sanity check. A 55W bulb at 12.7V should draw around 4.3A in theory, so anything between 4 and 5 would probably pass a sanity check. But I've never actually tested one before, so I don't know how literally to take the 55W nominal rating.

First off, what modulator are you using?

I have the SDC that can be used with Hi beam, low beam and turned off. That unit pulls through the leftside (yes, you have to use the leftside) headlight connector. So now you are powering both headlights through one circuit. Because it draws more power now, the headlights were dim at best! Swapping over to LEDs are a different story, although NOT approved for LEDs, the SDC unit works great with them, since the LEDs aren't pulling as much power through. But the problem with LEDs and this modulator, is that it flashes, instead of modulates.:duck:

There are plenty of other modulators out there. The one I first started with (Comagination), you had to setup your headlights off of a different power source, like a bluesea fuseblock and relay. It only modulated on high beam, and you couldn't shut it off! I'm not sure how it would work with LEDs.

STmark1300 said:

I have a modulator on my bike. They have run great for 2 years. Two times in two weeks I popped 2 fuses. I normally run with it on. I remember I am running the H4's. My questions is two fold. One, can the bulbs draw more as they age? Two, is 8there an led replacment yet? Alsp can I go to a 25amp fuse?

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I don't know about your modulator, but when I read your post the first thing that popped into my head was corrosion in a connector. Or, you have a wire that is vibrating causing the insulation to wear through, and is finally grounding out. Just my thoughts.

Soontobeone said:

Or, you have a wire that is vibrating causing the insulation to wear through, and is finally grounding out.

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yeah, that's what I meant when I said earlier you may have an intermittent ground problem. I didn't mean you were intermittently losing ground, I meant you were intermittently shorting something directly to ground, which blows the fuse because of excess current draw.

I too had a headlight fuse problem back in 2010. Look at the picture in post #97

The picture is taken in the area between the left inner cowl and the gas tank. Seems someone did not get the wire harness tied back where it belonged. When ever I did a full lock left, the wires got shorted out on the pointed post that the clutch hose is held in place with. Take a look, as two other bikes at this event had this same issue, but had not started to do the short out routine, yet.

To answer your first question, No, lamps do not significantly change their current draw over time (well, not exactly true - current goes to zero when the bulb burns out). If a filament breaks, and while waving around from vibration, touches the other support post and welds itself in place, this shorter filament will be different than a new lamp.

I think you should unplug the modulator, as dwalby suggested and see what happens.

I ran it two days with modulation turned off, and on low beam. It did not burn a fuse. Kevin, now that you say that, I remember that posting. That's possible I made those wires to short. And since it's intermittent seems possible...when I turn sharp. Taking off the crowl takes some time. I will probably pull the bulb first, see if the filament is OK. Also can I check the modulator by using a multi=meter across the fuse posts?

I used a Kriss modulator on '91 GoldWing , '05 Aero 750 , & the '07 ST1300 - the ST gave me fits , acted really bizarre , until I rewired the headlight bulbs to match the more conventional & logical wiring like the GoldWing has , then it all worked. ( look at wiring diagram of how the left & right bulbs get fed differently , what was some ST electrical engineer at Honda thinking ? ! )

TourNut said:

look at wiring diagram of how the left & right bulbs get fed differently , what was some ST electrical engineer at Honda thinking ? ! )

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Maybe independant circuits to reduce simultaneous failure? I don't really know. But I bet the engineer had a good reason. I don't see the design being designed for complexities sake.

Mine is a Kriss.

I always thought that the low beams draw less amperage. But now I'm not sure. Is that true. I could live with running the modulator on low beam.

STmark1300 said:

I always thought that the low beams draw less amperage. But now I'm not sure. Is that true. I could live with running the modulator on low beam.

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a low beam draws less but will not cause a fuse to blow. You have a classic symptom of a short to ground. When looking for shorts on a car if there has been any aftermarket stuff added that's where I start. I would turn the lights on, turn the bars end to end. Reach any of the wire harness and wiggle and slightly tug on it and see if you can get the fuse to blow. Inspect areas that has movement, handle bar area and recheck the wires for the modulator. You are looking for a power wire that may be shorted to ground. A corroded connector would increase resistance but not blow a fuse.

STmark1300 said:

Is that true.

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That depends on what bulbs you have in the ST.

The factory bulbs ST1300 are 45/45W so I assume that they draw very very close to the same current. If you throw in a non-factory bulb they'll likely be a difference in current draw such as a 55/60W or 55/100 90/130 etc and the low beams will draw less current.