The Main Fuse

[DonTZ125]

Ok, I stopped myself from hijacking Tech7's thread about blowing his main fuse, but I still have to ask - WTF does this fuse actually do?! Looking at the schematic, it's AFTER the VRR branches off to the main switch, so the only thing it should be protecting is the battery. It can't be protecting the starter or starter relay, since the alternator isn't turning fast enough at that point.

My reading of the schematic is that it should have absolutely no effect on the operation of a running motorcycle, but should only prevent one from starting once popped. Yet there have been several people (including Tech7) who've noted that a blown main fuse has shut them down.

What am I missing?!

[yamaha_george]

The Main Fuse

The main fuse does not protect the battery whatsoever, It protects the wiring from the battery up to the Ignition/Main switch (including the VR), then the Brown wire to the fuse box, also on US models (maybe others to), the Main fuse supplies power (VIA the main switch) to the Tail lamps and if fitted running lamps in the front blinkers, take a look @ the wiring diagram. On some European models power from the main fuse is used VIA a relay to power the Low beam bulb when the Hi beam is switched on, single headlamp, with dual bulbs, both low and hi beam bulbs are illuminated, when in the hi beam is switched on.


QUOTE:-
I think were you're getting confused, You're thinking of the VR as the power source, if so your mistaken the battery is the power source. Another thing the main fuse is in the wrong position on the harness a very poor design fault!!. Think about it if tail lamp blows and shorts out causing the Main fuse to blow, whilst your hurtling down the road. Kiss goodbye to the VR and all your bulbs, maybe more.

Sound familiar ? -Y-Geo.



you may ask why? the main fuse is connected battery side of the VR, if the fuse blows the VR has nowhere to dump its output i.e. the battery, diodes go POP = an overcharging VR.

Hmm that has a familiar FZR ring to it ---Y-Geo

Ideally for full protection another 30 amp fuse should be fitted between the VR and main switch, therefore if that fuse blows the VR is still connected to the battery and will survive.

Ooopnorth

UNQUOTE

[DonTZ125]

Hi, YG, Ooopnorth - I agree completely that the fuse is in the wrong spot, that it should be 'upstream' of the main switch.

I must however disagree that the battery is the power source of a running bike. My understanding is that the alternator and VRR provides the power to run the vehicle and recharge the battery. The battery is there for start-up, and for slow-running situations when the alternator isn't spinning fast enough.

I'm looking right now at the wiring schematic for the US '89 FZR600W; the FZR1000 and 400s are nearly identical in and around the components under discussion. Power to the main switch flows from the battery through the main fuse when the vehicle is off, certainly; this is how the markers are lit and the TCI powered up to get the vehicle started. When the vehicle is running, power flows (unfused) from the VRR to the main switch, but takes what is now a side branch to the battery via the main fuse. The voltage potential at the VRR (14.5v nominal) is higher than at the battery (~ 12.7v?), thus current (if any) flows from the VRR to the battery - with a charged battery and a functioning VRR, there should be NOTHING flowing through that main fuse!

I do note and acknowledge that the bLue wire from the main switch to the marker lights is completely unfused from the VRR; I assume the folks at Yamaha were as disbelieving as I that a 6W marker bulb could carry enough juice to a) pop a 30A fuse, and b) slag the VRR! That said - clearly, somehow, it happens.

My comment about protecting the battery is that - should the main fuse blow - the only components disconnected from the 'hot' side of the electrical system is the battery, starter solenoid, and starter motor. The main switch, TCI, lights - everything is still connected to the spinning alternator and the +ve lead from the VRR; the VRR is still connected to ground. There should still be a complete electrical path for the power from the VRR.

So, back to my original question - what does that 30A fuse do? Apparently, *nothing*. The 30A fuse should be between the VRR and the main switch, and there should be a 10A fuse in the bLue wire to the marker lamps.

Comments?

[olie05]

If you look at 2005 CBR600RR wiring diagrams it seems that the 30 amp fuse is placed between the VRR and the battery at the starter solenoid, and all other components are fused independently, and powered from the VRR side of the 30 amp fuse.

If for some reason the main fuse popped while riding, you would still be able to ride, since the VRR is powering the entire circuit, but once you turn the engine off (or stall), you wouldn't be able to actuate the starter relay. Seems to me like a "limp home mode" type of mentality. The 2009 monster 696 has a very similar setup.

Only difference from our bikes, I'm guessing, is a more robust VRR unit.

I also seem to remember seeing a motorcycle wiring diagram where the low power lighting took its power from the ECU, but I can't seem to find it now.

Also, I'm with Don on this one:

I think were you're getting confused, You're thinking of the VRR as the power source, if so your mistaken the battery is the power source.

If you want to get technical, the A.C. generator is the power source, the VRR is an AC to DC converter, and the battery is a power storage unit. The VRR/AC Generator is perfectly capable of operating the electrical system without the battery (once the engine is rotating). I found this out when I had no battery fluid in my battery for a week... I got really good at push starting the thing on my own!

Geo, you would be right if we were talking about a total loss electrical system.

[yamaha_george]

Ollie
In the race world total loss system is having no battery as you have found out it seems :-}

apart from that let me re-phrase some of what has been written:-
Q
Looking at the schematic, it's AFTER the VRR branches off to the main switch, so the only thing it should be protecting is the battery. It can't be protecting the starter or starter relay, since the alternator isn't turning fast enough at that point."
/
That statement leads me to believe that, your thinking the "Main fuse" protects the battery from the VRR. Which is incorrect, it's there to protect the wiring and VRR in case of a short circuit. If the fuse wasn't there, a short circuit on the Red, Brown or Blue wires or a faulty VRR (blown Regulator) would = melted wires, and more than likely a fire.

As stated earlier the Main fuse is a poor design fault. The ideal set up would be, VRR connected VIA a fuse (in case the Regulator fails, shorting to ground) to the battery side of Start Relay, then from the Start Relay again VIA a fuse connected to the Ignition/Main switch, and as Don quite rightly mentioned "there should be a 10A fuse in the bLue wire to the marker lamps."

The FZR 600 12 amp hour battery has a CCA (Cold Cranking Amps) rating of around 150 - 165. CCA equate to, the number of amps a battery @ 32 degrees F (0 degrees C) can deliver for a period of 30 seconds, I don't think the VRR can push out anywhere near 150 Amps. Therefore in my opinion the Main power source is the battery. Let's agree to disagree basically it's not that relevant to your question.

Getting back to blown bulbs causing a short, I admit it's rare but occasionally when a bulb blows it can short circuit internally, blowing fuses. If I ever come across a blown fuse that supplies bulbs, first thing I do for elimination purposes is remove all the bulbs connected to that fuse, it's much quicker that trying to trace a short in the wiring. I've came across this a number of times, the bulb was the culprit.
YMMV

[olie05]

Ollie
In the race world total loss system is having no battery as you have found out it seems :-}

On the contrary, total loss means running without an alternator, and reaping the benefit of reduced crank inertia and drag. This is the rare case where the battery is the main source of power to the rest of the electrical system.

http://www.google.com/search?hl=en&sour ... 1&aql=&oq=

...Which is incorrect, it's there to protect the wiring and VRR in case of a short circuit. If the fuse wasn't there, a short circuit on the Red, Brown or Blue wires or a faulty VRR (blown Regulator) would = melted wires, and more than likely a fire.

This is exactly Don's problem with the system, The main fuse does not isolate the VRR from the rest of the system in case of a short. It only has the capability to isolate the battery from the VRR and the rest of the wiring.

The FZR 600 12 amp hour battery has a CCA (Cold Cranking Amps) rating of around 150 - 165. CCA equate to, the number of amps a battery @ 32 degrees F (0 degrees C) can deliver for a period of 30 seconds, I don't think the VRR can push out anywhere near 150 Amps. Therefore in my opinion the Main power source is the battery. Let's agree to disagree basically it's not that relevant to your question.

Sent you a pm.

[DonTZ125]

As I said in the original post, "What am I missing?" The answer apparently is, "The wiring itself!"

Ok, YG says there should be 2x 30A fuses - one from the battery to the main switch (got it), and one from the VRR to the battery without involving the main switch (need it). I've been getting bits organized to start building adaptor harnesses to make the VRR upgrade a plug-and-play prospect; I will have a 4-pin male plug that connects to the stock connector, and a 6-pin female socket that hooks up to the new VRR. A dedicated black wire will be run back to the battery. It would seem that the new red wire, instead of simply connecting to the original 4-pin plug, should instead be run to the battery with an inline fuse!

(The original red wire would simply terminate at the stock 4-pin socket, with no mate in the 4-pin adaptor plug.)

Now, what's the simplest way to add a 10A fuse to the marker lamp circuit...

[olie05]

On the VRR, what i don't get is why aren't modern oem's putting a fuse between the VRR and the rest of the wiring, if it is such a problem? Is it possible that (newer) VRR's have an internal fuse built in?


For the marker lamp circuit i think simplest way is an inline fuse, between the tail lamp (where they get power) and the markers.


btw Don, I found your holy grail: http://www.motec.com.au/pdm15/pdm15overview/

[yamaha_george]

Total loss systems on bikes with electronic ignition that I have raced for some 30 odd years need no battery, the lighting systems coils removed and flywheels lightened if required.

What other people do / did I cannot say I just speak from experience not something I read

[DonTZ125]

YG - I see exactly what you're saying, but the definition of 'total loss' you're using is the opposite of what I (and obviously olie) are using, along with a lot of other people (suggested by his google link).

You're saying that all the power generated is lost, not saved in a battery. The more common definition (AFAIK) is that NOTHING is generated, that all power used is from a battery; it is thus lost, and your racing vehicle will at some point shudder to an ignominious halt if the battery isn't up to the duration of the race.


Olie - my reading of the wiring schematic and diagram is that the power take-off for the front markers is up at the switch, then running back to the tail bulbs. If the marker wiring goes to the tail bulbs first, then runs back to the front, then I would agree that the tail section would be a convenient place for a fuse.

[yamaha_george]

YG - I see exactly what you're saying, but the definition of 'total loss' you're using is the opposite of what I (and obviously olie) are using, along with a lot of other people (suggested by his google link).

You're saying that all the power generated is lost, not saved in a battery. The more common definition (AFAIK) is that NOTHING is generated, that all power used is from a battery; it is thus lost, and your racing vehicle will at some point shudder to an ignominious halt if the battery isn't up to the duration of the race..

Don,
Total loss systems on bikes with electronic ignition that I have raced for some 30 odd years need no battery, the lighting systems coils removed and flywheels lightened if required.

What other people do / did I cannot say I just speak from experience not something I read.

[taggy]

my bike is running what was called total loss by the previous owner. It has a battery but no genny coils or starter or charging circuit and has the starter gears removed and the crank balanced to compensate. I guess there must be a couple of different definitions used as i know i need a battery to run it. The fuel pump at least won't work without the battery! Perhaps in this case total loss is referring to the fact that the battery runs down and isn't recharged? totally loses charge??

[yamaha_george]

my bike is running what was called total loss by the previous owner. It has a battery but no genny coils or starter or charging circuit and has the starter gears removed and the crank balanced to compensate. I guess there must be a couple of different definitions used as i know i need a battery to run it. The fuel pump at least won't work without the battery! Perhaps in this case total loss is referring to the fact that the battery runs down and isn't recharged? totally loses charge??

Hi,
well that was not so hard was it, a guy who has a different experience of a race style system. Amen

[olie05]

Whatever floats your boat, Geo. I'm just surprised it took 3 people posting about total loss for you to realize that the rest of the world has a different definition.

Having wired 3 race cars, I would say that I qualify in having what you call "experience." (although I like to think i have much more than just that.)

Judging from what I've read on this forum, I wouldn't discount Don's experience/knowledge either.




...why do all threads on this forum end up on tangents?

[yamaha_george]

Whatever floats your boat, Geo. I'm just surprised it took 3 people posting about total loss for you to realize that the rest of the world has a different definition.

Having wired 3 race cars, I would say that I qualify in having what you call "experience." (although I like to think i have much more than just that.)

Judging from what I've read on this forum, I wouldn't discount Don's experience/knowledge either.




...why do all threads on this forum end up on tangents?

Ollie,
Again you have missed the point, I write about what I know from experience NOT what I have just read some place as I cannot confirm that it is a fact & not just an opinion.

The posts implied I was in error

I the definition of 'total loss' you're using is the opposite of what I (and obviously ollie) are using, along with a lot of other people (suggested by his google link).

what I stated was backed by 30 years of using a total loss system on my race bikes, that what other people did I had no knowledge of except by reading stuff that I could not confirm worked as I had never actually used it.

What people say they use is often not detailed enough technically speaking to be relied upon as being 100% accurate & therefor replicated safely.

Why do threads go off at a tangent ..........................

I will let you figure it out