Headlight On/Off Switch Semi-Bypass?

[Guest]

Salutations all,

I am in the process of reworking my 1980 GS450's electrical system as per the various recommendations I've found on and around the site.

I'm going to replace the bad stock Regulator/Rectifier with a Honda Shindengen SH532-12, and I have seen it repeatedly recommended that the stator be wired as directly as possible to the R/R to reduce resistance. However, this is typically discussed in the context of post-1980 models where the headlight switch is no longer functional and the excess wire running to it and back is therefore vestigial (and, the headlight being always on, all three phases of the stator are constantly in use).

My question is this: I intend to keep the functionality of my headlight switch, but would it still be ok to wire the R/R straight to the stator and just bypass that part of the switch? I know it's possible because it's a double pole switch and I could just skip that half; what I'm wondering is whether it's advisable.

A simple yes or know will do, but if you wish to check and/or correct my technical understanding, read on.

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My reason for concern is as follows:
As I understand it, one function of the headlight switch is to cut off one arm of the stator when the headlight (a major power draw) isn't functioning. So, in stead of making the R/R deal with all that extra juice when the light's off, that stator coil just has to eat up the induced voltage and (I presume) dissipate the engergy as heat. If I bypass this switch, it keeps any arm of the stator from ever being turned off (which, I imagine, is a relief for the stator), but then the R/R has to deal with that much more juice when the headlight is off. This worries me because I don't know how much the R/R can take, especially since any post-1980 R/R was probably engineered under the assumption that the headlight(s) would always be on.

Please forgive me if my understanding is crude. I've been through basic electricity twice, once in a physics class and once in aircraft mechanic training, but my insight into most electrical phenomena is still rudimentary.

[Mekanix]

You got it, the big difference is if you have a series or shunt RR, I don't know that model off hand.

The Stock unit would shunt all excess voltage and fry itself or the stator.

A series unit would simply not use the power if it wasn't necessary to maintain a good output voltage.

[bbytes]

Looking at the wiring diagram for my 1979 GS550L, which I assume is very similar to your bike, it doesn't appear that there would be any issue with wiring your headlight in an always on position. The headlight switch should have 4 wires in it. Connect the orange and green wires in a permanent connection. Leave the other two connected to the switch. If you burn out your headlight, then flip the headlight switch into the off position. Your understanding is for the most part correct, although I don't think it will hurt to have it on all the time. Just make sure that switch is always in the "On" position when the bike is on, or wire the other two wires to each other. What you don't want is the headlight on, but the R/R not running at full power.

[caltrop]

it doesn't appear that there would be any issue with wiring your headlight in an always on position.

I appreciate your feedback, but I believe you have interpreted my intentions in reverse. I'm contemplating leaving the headlight switched (can be turned on or off) and wiring the stator straight to the R/R (all three stator phases running to R/R all the time, as opposed to the original, switched, configuration).

[bbytes]

Well considering you legally need to have your headlight on, I still don't see a real issue. I don't think that turning the headlight off for a few minutes will blow it, but it would probably be better to not risk it.

[posplayr]

the primary reason you want to wire the stator directly to the R/R (and NOT go through a ganged head lamp switch) is that the current flow through the stator is significant (approx 5 amps AC per leg)and it is hard to keep clean connections for all the additional wire and connections required to route up through the LH switch. That means those wires tend to get hot at connections and the wire gets brittle and it all goes down hill from there.

Your understanding of what the R/R is doing is not quite right. There are descriptions here and in the manual. A SHUNT R/R shorts across a pair of stator wires in which case the current in the stator spikes. A SERIES just opens the winding which means the current drops to zero during regulation.

[Steve]

I did basically what you are asking about on my son's 650L. OK, the 650 never had a headlight switch, it was taken from a 450 when the 650's switch broke. We turn the light off while starting the bike, then leave it off for a few minutes to charge the battery quicker, but turn it on before hitting the road. Works quite well when used that way.

.

[caltrop]

A SHUNT R/R shorts across a pair of stator wires in which case the current in the stator spikes. A SERIES just opens the winding which means the current drops to zero during regulation.

Thanks for the clarification. So a series opens a winding, which, as I understand it, is what the headlight switch currently does too.

A shunt, it sounds like, shorts across a resistance (though I guess a lower resistance than that of the system in general, hence the current spike) and dissipates the energy as heat. (If I still don't have this right, please do correct me, I'm always happy to learn .)

I can't say I know which type the SH532 is, nor have I been able to find a concrete source that would tell me one way or the other.

I feel like, if it were a series R/R, the switch would simply be imitating the R/R in a "dumber," less automatic, fashion, so it seems like going the low-resistance route and bypassing the switch wouldn't be much of an issue.

If it were a shunt, I guess the question is whether that extra current could be handled by the R/R or stator.

One of the R/R Replacement List threads informs me that the 532 has a 35 Amp rating. A post on a completely different forum said that this was the shunt current it was rated for, but the fellow didn't sound particularly confident in his conclusion, and I'm having trouble finding any sort of confirmation that that's what that means. Sorry, I don't know very much about R/R specs. Kinda dumb sometimes

[posplayr]

Thanks for the clarification. So a series opens a winding, which, as I understand it, is what the headlight switch currently does too.

A shunt, it sounds like, shorts across a resistance (though I guess a lower resistance than that of the system in general, hence the current spike) and dissipates the energy as heat. (If I still don't have this right, please do correct me, I'm always happy to learn .)

The series just does it much faster that the headlamp switch and it is balanced on all three legs not just one like the headlamp switch.

See simplified explanation here. SERIES is th4e way to go if you can afford it.

SHUNT_vs_SERIES_RR_Compare_Tutorial
http://www.keepandshare.com/doc/4066862/ssr-vs-fh012aa-pdf-may-31-2012-10-20-pm-903k?da=y

[caltrop]

Okay, so it appears to be a shunt type. Whether or not this rewiring would be advisable would then, it seems, depend on the amount of heat the R/R is capable of dissipating and the amount of current it lets go through the stator windings when it's shunting (so basically it comes down to the size and rating of the resistor(s) it shunts through, yes?). Does anyone have any insight as to how I might be able to get some specs on this thing?

[posplayr]

Okay, so it appears to be a shunt type. Whether or not this rewiring would be advisable would then, it seems, depend on the amount of heat the R/R is capable of dissipating and the amount of current it lets go through the stator windings when it's shunting (so basically it comes down to the size and rating of the resistor(s) it shunts through, yes?). Does anyone have any insight as to how I might be able to get some specs on this thing?

If you want to reinvent the wheel than continue on.

If you care to take any advice get rid of the stator wires through the headlamp switch.