Headlight Fuse is Melting, not breaking but MELTING!

[Motorbreath]

ok

i thought that a bad wire would cause an increase in load in the same as say heated grips cause an increase in load.

Yes, the heated grips are in parallel, so they decrease the resistance of the complete circuit. (current runs both thorugh the original circuit and the new grips circuit)

As some one said earlier in the thread heating is due to increased resistance or load if the bulbs are standard and in good order I would suspect a poor conection - Its a simple enough circuit so I would check and clean the conections and put in a new fuse.

You can never rule out the PO factor ( previous owner) - my wiring was getting real hot when on full beam - on inspection the main beam on one bulb had a wire soldered on it linking it to the un used dipped fillament - way too much load - again strangly didnt pop a fuse but the bulb connectors started to melt!

As said before, resistance reduces heat. As you describe it probably you had both H4 filaments enlightened, that caused the excess of heat. Your fuse couldn't break because there wasn't more current thorugh the circuit, actually there was a bit less. The normal headlight mod we all do increases current as both bulbs are in parallel (but just one H4 filament), but still it is not enough to melt the fuse or anything else.

Again that strange word "load". I do not understand what you mean, but it seems it causes confusion. I do not know even how to translate it to Spanish when talking about electrics.

http://www.aeroelectric.com/Mfgr_Data/Fu..._Specs.pdf

Here you go, all you need is a multimeter set on DC amps in line with the circuit and you see what's happening.

It seem fuses apply the 80% rule. It means a 20A fuse can melt if it has 18A running all the time? But he measured only 10A already, mayby he is wrong.

Hey everyone, thanks for all of your responses, I'll change the bulbs and then do a more thorough check of all the connectors and wires in the circuit.


@unfazed
I do have a modded headlight but the problem still occurs when I disconnect the wire, it even does it when just the side/tail lights are on so I'm not sure it's an issue.
Thanks

What mod? Did you replace the fuse?

[JZS 600]

The fusing element must not hinder the normal circuit path, but it must also overheat and melt in response to excessive current (overcurrent). In simplified terms, the melting function depends upon the power expression of P = V * I, where P is the power in Watts. By algebraic substitution with Ohm's Law, the expression becomes P = I[sup]2[/sup] * R, showing that a linear change in current produces an exponential change in power dissipation, which is useful in a fuse. But how quickly should the fuse respond? Fast? Slow? How fast or slow? The capabilities can be summarised with a TCC (Time/Current Curve). A logarithmic scale is typical, with current shown on the horizontal (x) axis and time on the vertical (y) axis. The TCC in Figure 1 is illustrative of a very fast 1A fuse. First, we observe that no fuse of this type can fail from overcurrent until at least 1.25A is flowing, and none is guaranteed to fail until 1.5A is achieved, or 150% of nominal current. A factor of 1.5 is rather optimistic, and many real-world fuses are more in the range of two, representing the safety factor that must be allowed when a fuse is specified.

[img alt=Figure 1]http://sound.westhost.com/articles/fuse-f01.gif[/img]
Figure 1 - Possible TCC for a 1A fast-acting fuse

Second, note that the TCC is a region representing unavoidable variations, since a thermal melting mode cannot be precise with real-world materials. Here, one fuse might pick up at 1.25A and fail, i.e. clear the fault, in about ten seconds, and another fuse may not clear until 1.5A flows for ninety seconds. The gap between the nominal current rating and the minimum trip is also unavoidable, as a minimum trip too close to the nominal rating would subject the fuse element to large, thermally-induced mechanical stresses during normal operation. The curve characteristic is maintained in a family of fuses. A 10A fuse of the same family would yield a similar curve, but shifted right, with an initial pickup from around 12.5-15A. For any fuse, three data points are particularly interesting to a hobby user:

• Voltage Rating: When a fusing element separates under load, an arc can strike in the gap. Current flow is sustained by the arc, and the element may weld back together for a second break, or the arc may persist and continue melting the element outward. The voltage rating specifies the maximum voltage for which clearing can be guaranteed. The voltage rating must account for all possible failure conditions including the limits of the dielectric medium (type and degree of physical separation between ends), vaporised metal products formed in the chamber, and any support structures that may allow the arc to "track". AC ratings are usually higher than DC ratings since the zero-crossings accelerate the arc collapse. Fuses intended for 12V DC automotive electrical systems usually have a 32V DC rating. The AC rating is often 250V, but this cannot be assumed if data are not available to prove it.
  
  
  
• Current Rating: The nominal rating is the maximum current the fuse can carry continuously. A correctly specified fuse should have a long service life, but an overrated fuse may not protect the circuit if the required safety factor current exceeds what the circuit can source in a typical failure mode.
  
  
  
• Timing Characteristic: Smaller fuse styles will specify "fast acting" (FA) or "slow blow" (SB, or Time Delay) and not provide a TCC. Fast fuses are intended for applications where any failure condition must be quickly interrupted. Time delay fuses are useful when a momentary overload may legitimately exist for a short time (motor or transformer startup) and cause nuisance tripping of a fast fuse.
  

A nuisance (fatigue) failure occurs when the fuse has been aged by numerous operation cycles, or the fuse is operating slightly above its nominal current rating, or the fuse is subject to abuse such as inrush spikes or even mechanical vibration. Metal fatigue from aging is normal, but the latter cases can indicate a system design problem or an insufficient fuse rating. A fuse that is being run slightly above its current rating, or stressed by an inrush, can often be observed to move inside the cartridge. It may survive a number of cycles but it will eventually fail.

[JZS 600]

Or just give everything a good going over with contact cleaner  :lol

[Fazerider]

This sounds like a poor connection, probably to one of the blades of the fuse.
Check the connectors are clean and tighten them... it should require a noticeable amount of force to shove the fuse in. If that's not the problem then the cable, where it joins to the connector may have corrosion or a few broken strands, in which case you'll need to remake the end.
The problem is indeed too much resistance where there shouldn't be.
As others have been pointing out, that will result in less power... but only from an overall point of view. If the contact resistance to one end of the fuse is, say a tenth of an ohm, that will lose a volt across it if the current is 10 amps... the lights will then be working from a volt less, but the current won't reduce by much as a result... even if they were simple resistors it would only be a 9% drop (in fact they're non-linear resistors... they'll be a little bit cooler and yellower so their resistance will also have dropped a bit).
So the headlamps are dissipating a little bit less power, but the poor old fuse is now trying to get rid of 10 watts (resistance x current squared = power) as a result it gets hot enough to melt the plastic.

[clayt74]

This sounds like a poor connection, probably to one of the blades of the fuse.
Check the connectors are clean and tighten them... it should require a noticeable amount of force to shove the fuse in. If that's not the problem then the cable, where it joins to the connector may have corrosion or a few broken strands, in which case you'll need to remake the end.
The problem is indeed too much resistance where there shouldn't be.
As others have been pointing out, that will result in less power... but only from an overall point of view. If the contact resistance to one end of the fuse is, say a tenth of an ohm, that will lose a volt across it if the current is 10 amps... the lights will then be working from a volt less, but the current won't reduce by much as a result... even if they were simple resistors it would only be a 9% drop (in fact they're non-linear resistors... they'll be a little bit cooler and yellower so their resistance will also have dropped a bit).

So the headlamps are dissipating a little bit less power, but the poor old fuse is now trying to get rid of 10 watts (resistance x current squared = power) as a result it gets hot enough to melt the plastic.

Have to absolutely agree with Fazerider,
I am assuming when you measured 10A current the fuse was removed and your meter was across the fuse contacts?
10A is about right for a good loom with 2 off 55w bulbs, not sure how you measured 70 ohms tho??? 2 bulb filiments should measure about 0.7 ohms!!!
sounds like you were measuring the additional resistance of poor contacts between the fuse and fuse holder which as Fazerider says is responsible for the volt drop and excessive heat across the fuse.
only other cause is that the fuse itself has excessivly fatigued and has built up its own internal resistance (rare but can happen)

[willmckeand]

Have to absolutely agree with Fazerider,
I am assuming when you measured 10A current the fuse was removed and your meter was across the fuse contacts?
10A is about right for a good loom with 2 off 55w bulbs, not sure how you measured 70 ohms tho??? 2 bulb filiments should measure about 0.7 ohms!!!
sounds like you were measuring the additional resistance of poor contacts between the fuse and fuse holder which as Fazerider says is responsible for the volt drop and excessive heat across the fuse.
only other cause is that the fuse itself has excessivly fatigued and has built up its own internal resistance (rare but can happen)

The 10A was measured across the fuse contacts with the fuse removed, i thought that sounded about right too. I measured the resistance across the fuse contacts also, but I was a bit unsure of which setting to have the multimeter on (200, 20 etc)


I've replaced my H4 bulb and the fuse doesn't seem to be heating up as quickly as before, just gets slightly warm and stays there, but I'll check properly on my commute tomorrow.




@unfazed, I usually have a wire running from the live feed to my H1 bulb to the upper live contact on my H4, so that both lights are on when I have my lights on dipped beam and the second filiment of the H4 comes on when I switch to full beam.


I've gone through several fuses in the past couple of days because I don't want to use ones which look damaged or melted when I'm testing the circuit for problems.




So again thanks everyone for taking such an interest it's really appreciated and I'll see how it goes with the new H4 bulb tomorrow! 

[unfazed]

I have seen dual filament bulbs blow and the blown filament fall across the legs supplying the filaments and create a short circuit but still appear to work. If changing the bulb does not solve the problem then you need to visually check the wiring loom and all connections from the headlight back to the fuse including the internals of the switches for short circuits to earth.
this is a check you could do. With the ignition off remove the fuse,  set the meter to Ohms, Check the resistance between the supply to the switches (non live side) and earth with the left hand switch set to dims and the on/off light switch (right hand switch) Set to off:  resistance should be in at least in 100KOhms range or higher (keep your fingers away from the probes as for infinity your fingers will effect the reading.
Set to park centre position: resistance should be less than 4 ohms. You are checking the resistance of the parking light bulbs (Front and rear) and meter light bulbs in parallel.
Set to fully left position:  resistance should be slightly less as your including the dims in the check
Switch dims to heads and see what the readings are should remain around the same
If readings are less than 1 to 2 Ohms you have a short circuit somewhere.
If readings are very low disconnect the headlights one by one and see if the readings increase. Now remove the parking light bulbs front and taillight bulbs rear the readings should increase again as it is only the meter bulbs are being measured.
These readings are not exact as I do not have the 00/01 Fazer to check them.
If anybody has a 00/01 Fazer and a meter they could do the checks above and list the readings for you.
Let us know how you get on.

[Fazerider]

Will, I really wouldn't recommend wiring the r/h main beam that way.
It's much better to do the mod as detailed in the "Articles" section rather than having both main and dipped filaments lit simultaneously. The extra heat risks cooking the coating off the reflector.

[willmckeand]

Did my half hour commute today with the lights on with no problems thanks to a new H4 bulb! A couple of months ago I noticed that there was a wire bridging the H1 and the H4 but one end had been disconnected, so I re-connected this dodgy headlight mod, which as Fazerider points out is not a good as the proper one.


I've had it like this for over two months I think what must've happened was that over time the extra heat from having both filaments lit simultaneously has deteriorated the bulb, somehow increasing it's resistance thus melting my fuses.


Lesson learnt, and a set of Osram Nightbreaker Plus H1 and H4 on the way to hopefully improve the terrible headlights of our dear FZS600's.


Thanks again everyone for your input, I'll be sure to return the favour on here if I can one day!


Will

[andybesy]

Let us know how the new bulbs works out.

[JZS 600]

Great!


Question though, if you are travelling at 70 MPH with your head lights on, what is the speed of the light coming out of the head lamps? 

[Motorbreath]

Great!


Question though, if you are travelling at 70 MPH with your head lights on, what is the speed of the light coming out of the head lamps? 

:lol If it's a Fazer, Warp factor 1

[limax2]

Great!


Question though, if you are travelling at 70 MPH with your head lights on, what is the speed of the light coming out of the head lamps? 

At 70 in the dark with the square eye'd Fazer it feels like you have already overtaken the light beam  .

[Fazerider]

[quote author=JZS 600 link=topic=5187.msg45304#msg45304 date=1352228403]
Great!


Question though, if you are travelling at 70 MPH with your head lights on, what is the speed of the light coming out of the head lamps? 

At 70 in the dark with the square eye'd Fazer it feels like you have already overtaken the light beam  .
[/quote]
:rollin

[willmckeand]

3x10[sup]8[/sup]ms[sup]-1 [/sup] :rolleyes  cannot wait for my new headlight bulbs! Also waiting on some crash protector bars and maybe one of these:


http://www.amazon.co.uk/Pyramid-Fenda-Ex...253&sr=1-3


should keep some of the crap off of my downpipes!