Charging system diagnostic leads failing head lights on '83 GS750ED

[Scottyg]

I'm riding a beautiful GS750ED, which runs great, but my battery has been dying on me. A friend suggested checking out this helpful site, which led me to the Stator Pages and a diagnostic chart. I tested the stator voltages and tomarrow will check the RR for my charging problems, but after I checked the first 2 of 3 tests I noticed my headlight stoped working. My high beem still worked, but then failed with some rpm's.

Does anyone know how the headlight system is linked to the 3 yellow wires leading to the stator, and how I could have shorted, or overloaded, the system with my multimeter?

Thanks, this site is already a big help.

Scott.

[silverhorse47]

There is a spec for how much voltage should be passing between each pair of the three yellow wires that come from your stator when your bike is running. It sounds as though one of these pairs...ie one winding of your stator...is 'open' ie it has a break in it. One of the windings takes excess voltage (that would burn up the battery if it were to receive it for charging purposes) and directs it to the headlight.

It sounds as though the leg of your charging circuit that protects your headlight is kaputty, though my understanding of all this is a bit slim.

S.

[txironhead]

Before you fry any more components, disconnect the regulator and try to do your tests with it disconnected.

Suzuki GS regulators have a strange "overload" circuit that sends excess voltage to the headlight. Apparently this is why some GS's have "off" switches on the headlights. It sounds like (but don't take me 100% on this) your regulator is fried. I would highly recommend doing the Honda R/R conversion that is outlined on this site. Just do a search for "Honda regulator" and you should find it. Honda regulators are MUCH better designed and last a lot longer than the factory Suzuki, and they eliminate the circuit to the headlight with no ill effects. Plus, they're cheaper!

Modifying electrical things may scare the screamin' willies out of you, but trust me, this is a very straightforward conversion that shouldn't take more than an hour with a common Honda CM400 or similar regulator.

[nabrams]

You've got the classic over-voltage scenario: R/R is letting too much voltage through (burning lights out in the process), but not enough to blow the fuse(s). Sometimes these old fuses don't blow when they're supposed to. Or, the fuse for those lights may have blown as they should and that's why your lights are out (you may have separate fuses for various electrical components).
Anyway, disconnect the R/R, run the bike at 5000 RPM and check the output of the R/R. If it's more than 15 volts then you know your R/R is toast.