Eletrical issue

[MoA-Biomass]

Good afternoon,
I have an Eletrical question for anybody in the know.
My ignition main feed fuse has blown again.
This fuse was changed in July last year and had semi melted.

This year I have been out once with no problems but just went to start and the clocks reset but then no start. Again the fuse checked and found blown.
Any ideas will be greatly received.

Cheers

 

[skydog1000]

Sounds like you have short @DEcosse Can you take a look at this

 

[DEcosse]

Let's start with what year/model and which # fuse specifically

 

[MoA-Biomass]

UOTE="skydog1000, post: 507455, member: 3953"]Sounds like you have short @DEcosse Can you take a look at this[/QUOTE]

 

[MoA-Biomass]

the Fuse marked with the arrow was melted.
I only no my bike as a rocket 111 built 2006 thats all it says on logbook. not a tourer

 

[DEcosse]

... My ignition main feed fuse has blown again.

OK - Fuse 11 is the MAIN Fuse, while the "Ignition Main Feed" is Fuse #2.

This fuse was changed in July last year and had semi melted .....

When you say "semi-melted" - do you mean the plastic body of the fuse was melted and distorted?

Like this:

When a Fuse blows from over-current condition (normally the circuit has experienced a momentary short to ground) then the internal fusable link simply opens, with no visible external damage to the body of the Fuse.

However if the plastic body is melted (like images above), that is from ongoing heat condition - although the quality of the fuse itself might be questionable, this is primarily caused in the first instance by poor connectivity of the fuse blades in the socket - a high resistance joint creates a volt drop across the fuse and an associated generated power which is expended as heat.
The best solution here would be to bypass the Fuse location in the Panel and replace with an external high-quality Fuse Holder connected to the original wires to that location in the Fuse Panel.
i.e. cut the wires going to OEM Fuse 11 and wire in a new Fuse Holder

p.s. While the situation is not caused by OVER-current, the generated heat is proportional to the AMOUNT of current - so it's important not to exacerbate the issue by having higher than OEM load connected - i.e. no High Wattage Bulbs or similar or accessories that have been connected without using a relay.

You can also reduce the current through that fuse significantly by installing a headlight relay kit, to bypass the current from that circuit (and also your key-switch which is the next point of common failure!)

 

[MoA-Biomass]

Mine was the one on the right.

 

[Mittzy]

OK - Fuse 11 is the MAIN Fuse, while the "Ignition Main Feed" is Fuse #2.



When you say "semi-melted" - do you mean the plastic body of the fuse was melted and distorted?

Like this:

When a Fuse blows from over-current condition (normally the circuit has experienced a momentary short to ground) then the internal fusable link simply opens, with no visible external damage to the body of the Fuse.

However if the plastic body is melted (like images above), that is from ongoing heat condition - although the quality of the fuse itself might be questionable, this is primarily caused in the first instance by poor connectivity of the fuse blades in the socket - a high resistance joint creates a volt drop across the fuse and an associated generated power which is expended as heat.
The best solution here would be to bypass the Fuse location in the Panel and replace with an external high-quality Fuse Holder connected to the original wires to that location in the Fuse Panel.
i.e. cut the wires going to OEM Fuse 11 and wire in a new Fuse Holder

p.s. While the situation is not caused by OVER-current, the generated heat is proportional to the AMOUNT of current - so it's important not to exacerbate the issue by having higher than OEM load connected - i.e. no High Wattage Bulbs or similar or accessories that have been connected without using a relay.

You can also reduce the current through that fuse significantly by installing a headlight relay kit, to bypass the current from that circuit (and also your key-switch which is the next point of common failure!)

How can you tell if the fuse is a good quality one with hi temp plastic?

 

[DEcosse]

Something like this would be a good replacement choice - Maxi Blade Automotive Fuse Holder

That is a Maxi-Fuse rather than an ATO/ATC size - will give you better blade contact (lower resistance) - this type (without wires) is going to be a better option than having t splice wires together
- however you WILL need a proper crimp tool to properly connect the terminals to the wires.

 

[DEcosse]

How can you tell if the fuse is a good quality one with hi temp plastic?

So that seller is essentially saying their plastic is better, so you won't have the problem - the REAL problem is not having the heat to begin with, rather than a Fuse that can withstand higher temperatures.
Fuses should NOT get hot!
Again, if it's getting hot, the source of that heat has nothing to do with the quality of the plastic, but to the quality of the connection between the blades of the Fuse and the sockets it sits in.
The sockets could be simply oxidized or they could be weak in their spring action, causing poor (high) contact resistance.
I don't know of anywhere to find the OEM Fuse Terminals, so the simplest solution is just to wire in a replacement external Fuse.
Note that Fuse carries pretty much all the load from the bike, which can include not only the headlights, but fuel pump, cooling fan, accessories connected to the OEM connectors.

The expended power dissipated by the Fuse comes from I^2 * R (Current Squared times Resistance)
The lower the resistance, the lower the dissipated power.
Also note that for any given resistance, the power is proportional to the square of the current.

Let's say the current is in the order of 20A - even if the contact resistance is only 0.01 ohms, then that still makes for 4W of power (equivalent to a parking bulb - and you know how warm that gets); if the resistance is higher, then the dissipated power rises accordingly.
So lower current will also mean that the expended heat will be less (you can't eliminate current, but you can make it go through an alternative bypass route e.g. headlight relay kit)

The other thing that can help is to lower the contact resistance - hence the proposed selection of the maxi-fuse, which has much bigger blade contact area (therefor inherently lower resistance than a physically smaller format)

Footnote: this is primarily only an issue with the classics - the Roadsters do not have the same configuration
(Touring do to some extent, but their current is less from the single headlight - on those bikes their weak link is the in-line connector from the battery - same problem, just a connector rather than a Fuse)