Why does Suzuki split R/R + output between ignition and battery?

[bwringer]

I also believe you are correct in noting the R/R will start pumping out max voltage, but I'm unclear if that would hurt the system in any way.

When R/Rs run amok, the max they will put out is around 17V. This will start blowing light bulbs more quickly than normal and boiling the battery dry eventually, but the bike will continue to run normally for many, many miles. So it's not enough of an overvoltage to destroy anything right away.


On my VX800 (same basic electrics as a GS), the regulator would stop regulating only when it was above a certain temperature. It took me several months and about five burned-out headlight bulbs to finally catch the bike overcharging and understand what was happening. Fortunately, the sealed Wally World battery wasn't damaged because the failure was so intermittent. I replaced the R/R with a Honda unit relocated from the idiotic stock location (right next to a hot exhaust pipe). Then a few months later, the overstressed stator finally gave up, but this was expected...

[Nessism]

I am looking at a wiring diagram right now. If I go straight to the battery and the main fuse blows, the Battery no longer has power to supply to Ignition Switch, which cannot supply power to the other 3 fuses, and the engine dies, the bike shuts down, including the lights.
OTOH, if I keep it in the loop and the main fuse blows, the R/R is still supplying voltage to the Ignition Switch, which in turn supplies the other 3 fuses, so the bike keeps running. However, the R/R now believes the battery is severely undercharged and goes through the roof. And there is no fuse to protect the system any more.

I believe this is correct. Suzuki's wiring method has a safeguard to avoid a complete electrical shut down in case the main fuse blows. I also believe you are correct in noting the R/R will start pumping out max voltage, but I'm unclear if that would hurt the system in any way.

I would really appreciate responses to this. If I have read/interpreted the schematic incorrectly, please tell me and explain how. I do not mind being wrong; it won't be the first time. Just show me the way and I will follow. I traced this using 650, 850, VX800, and 1100E wiring diagrams. If you have a different model, as long as our good friend BassCliff has the Service Manual on his website, I will download it and trace the wiring diagram for that particular bike.
I would like to understand all the ramifications of removing the link from the R/R to the Ignition Switch. If I do this, there will be both a 20A fuse and a 20A bimetal breaker between the R/R and the battery. The Main Fuse will also be upgraded to 20A, since it could now carry the entire output of the R/R. (More on this later.)
All I have really done is take a wiring diagram and trace everything out, with the unfused Ignition Switch link included (OEM) and with it removed.
If I am incorrect, LMK, and explain why/how. I will gladly accept your response(s) and investigate. If I am correct (it does happen on the rare occasion) LMK also.
Thank you in advance.

Thanks for the replies. Allow me to respond in order received:
bakalorz - If I do this, I will place a 20A fuse between the R/R and the battery. I also have an LED voltmeter which glows in different colours, according to the voltage:
Voltage
Output
>15.20
Green/Red alternating (over-voltage)
>13.20
Green (charging)
>12.45
Amber (75% plus)
>12.25
Red slow flash (50% approx)
>12.00
Red 2 flashes, repeat
>11.80
Red 3 flashes, repeat
<11.80
Red 4 flashes, repeat

I believe that the combination of these two safeguards will be sufficient safeguards to warn me if an overcharging occurs.
However, I believe you might be a bit confused. I am looking at a wiring diagram right now. If I go straight to the battery and the main fuse blows, the Battery no longer has power to supply to Ignition Switch, which cannot supply power to the other 3 fuses, and the engine dies, the bike shuts down, including the lights.
OTOH, if I keep it in the loop and the main fuse blows, the R/R is still supplying voltage to the Ignition Switch, which in turn supplies the other 3 fuses, so the bike keeps running. However, the R/R now believes the battery is severely undercharged and goes through the roof. And there is no fuse to protect the system any more. Please correct me if I am reading the diagram wrong.

Matchless, you are correct. In OEM configuration the supply from the R/R to the ignition switch is not fused. Please see previous reply.

OldVet66, you are correct. If the main fuse dies you are done.

Let me theorize a bit further if I may: In my TransAm I place relays everywhere it is very important to keep maximum power available. Each relay is fused in case things get out of hand. Where I really, really care, I also place a bimetal breaker in series with the fuse. If it overheats, the metals expand away from each other and the circuit broken. If I do this, there will be a bimetal breaker in place also.

I am really attempting to understand and grasp this circuit, so please LMK if I am mistaken in some area.
Thank you.

I would imagine the main reason for wiring it that way would be so the headlight does not go out if the main blows. I am considering wiring mine direct and using circuit breakers.

Oops, did not read it properly, thought it was loop through light switch!!
Old age does that they say!

On your original question, there are some theories around, but the fact remains that the supply to the ignition switch from the R/R is not fused while the other leg to the battery is protected by the main fuse.

Edit: Martin beat me to it. It is as he says!

The only advantage that I can see in that scenario is that if, for some reason, the MAIN fuse blows after the bike is running, the bike still gets full power from the R/R. The battery won't charge, but the bike will run.

<snipped rest>

.

I would STRONGLY advise NEVER letting the bike continue to run on the R/R output if the main fuse blows.

The R/R regulates by alternating between letting the full current/voltage of the stator through in pulses and comletely shunting it.
The battery acts as a giant smoothing filter or capacitor to keep the voltage near an average.
(even a completely shot battery that is no where near capable of starting the bike will still provide this smoothing)

When the main fuse blows, the battery is no longer in the circuit ... and no longer smoothing out the pulses.
So the voltage to the rest of the system is bouncing between 0 volts and significantly more than 14 volts ...

This doesn't seem to harm the lights, but it apparently is potentially BAD news for the ignitor.

If you search previous threads, you will find 3 or 4 threads where people blew the main fuse (or uninstalled the battery), push started the bike to get home, and ended up with a ruined ignitor.

Umm, thanks for the reply. That was an excellent explanation as to why one of the three phases of the stator went through the headlight shell. Unfortunately, that is a different question.
I am asking about the output of the R/R: "For some reason Suzuki splits the R/R positive output and sends juice into both the ignition switch and the fuse box...which then goes over to the battery."
Thank you.

I would like a thorough understanding of the ramifications of removing the loop through the ignition switch.
Thanks.

Just some background info. If look at the service manuals from the early 80's they show different schematics for the R/R internals. In many cases some R/R's of the era only regulated one phase sometimes two, nowadays all three phases are regulated.

Suzuki was also the only manufacturer that used specific coloured wires for each phase instead of 3 yellows or 3 whites. The reason for this was that they did not want the regulated phase to be switched in and out on the light switch, but specifically the unregulated phase.
A few years on, regulation on all three phases became the norm and such provision was not important anymore. Unfortunately the fact that parts such as regulators were in some way interchangeable and newer ones superceded the old type and they may have had a huge amount of spares out in the stores they retained the distinctive wiring.

At that time electronic components were quite bulky, especially if they had to handle a lot of heat and also expensive. It was thus easier and cheaper, or seemed so to them, at the time to not regulate all 3 phases.
They used the approach that if you "disconnect" one phase of the AC to the R/R, you in fact reduce the output capacity of the alternator by one third and if you are not using the headlight, two thirds of the output capacity should be more than enough to provide all the current the bike needs and have enough left over to charge the battery. The one or two phases then regulated would ensure that the alternator output is regulated as needed. With the lights on, the headlamp and other lights (55W + 10W + 3W+ 3W+ 3W = 74W) would immediately use the additional 6A and the regulation will still happen as when the lights were off.

Legislation changed in some countries and required lights on at all times and in other countries it was not required. In the USA they did away with the light switch to comply and retained the light switch on exports to other countries. The harnass was kept the same so they just bridged the USA bike wires that would have gone to the light switch at the plug.

The rest you should know...
This may not be 100% what they thought and why they did it at the time, but gives you the picture.

I just found this thread, and I would like to continue the discussion, please. If this has been gone over before, could someone please point me to the previous thread. I would like a thorough understanding of the ramifications of removing the loop through the ignition switch.
Thanks.

Nessism, you won't regret the switch to the Compufire system. I've got a set of the Weatherpack crimping tools on the way. I'll post up some links to pictures when I install the sealed weatherproof connectors.

[duaneage]

I saw a bad suzuki regulator pop the main fuse as soon as the bike started. The regulator shorted to ground as soon as the ac voltage hit the RR.

[Steve]

non enough info there Ed. Where is the load?

Agreed. If you ignore the load, that is exactly the same as Suzuki's wiring.

The difference would be whether the load is on the R/R side or the battery side of the main fuse.

.

[posplayr]

So if Suzuki's system is better how come Honda routes the power like this?

non enough info there Ed. Where is the load?

[Nessism]

So if Suzuki's system is better how come Honda routes the power like this?