Low voltage with headlight on, fine when off

[Guest]

Last year, when I picked up my 79 850, I ran it through the gamut of stator and r/r tests. My solution was to replace the r/r with a newer 50 amp unit and then other things in my life took priority. Unfortunately, I wasn't able to do much more with the bike until recently.

I purchased a $2 voltmeter (which gives +/- .1 v, not too bad) and wired it in semi-permanently off the fuse box (so, switched power source). This lets me keep an eye on the electrical system fairly well.

Down to the problem:
I get 11.6v with the headlight on at idle (1100 rpm give or take), 12.2v at 2500, 12.4v at 5000. However, with the headlight OFF, i get 13.1v at idle, 14.3v at 2500, and 14.6 at 5000.

I've read through some of the forum and I can't really nail down what I'm supposed to be looking for. My thoughts are that it could be a bad connection in the headlight loop, or a bad leg in the stator (though I ran through the stator resistance/continuity test last year and it passed).

I visually checked all the headlight connections and didn't notice any that looked badly corroded or burnt/melted. I have replaced the fuse box with a spade-type box along with a few inline fuses where appropriate.

Thoughts? I suppose after writing this it is fairly obvious that I should check voltage at the battery at the same time and re-run the stator tests (minus the r/r specific ones since I think those won't work on newer r/r's?)...


EDIT: of course, after creating this thread I found another post that seems to very similarly describe my issue (although that post is still open and unsolved): http://www.thegsresources.com/_forum...d.php?t=207982

[rustybronco]

Down to the problem:
I get 11.6v with the headlight on at idle (1100 rpm give or take), 12.2v at 2500, 12.4v at 5000. However, with the headlight OFF, i get 13.1v at idle, 14.3v at 2500, and 14.6 at 5000.

I visually checked all the headlight connections and didn't notice any that looked badly corroded or burnt/melted. I have replaced the fuse box with a spade-type box along with a few inline fuses where appropriate.

There is more to the 'system' than the headlights connectors in the headlight bucket. The four bladed connector at the ignition switch is one of them.

(1) check charging system.
(2) get wiring diagram.
(3) report back here.

[posplayr]

The other thread you mentioned fixed the problem by fixing the battery. In your voltage testing (which appears to be a variation of the quick test) you completely skipped the battery test portion . Had you done that the solution may have become more clear.

[jeff.saunders]

What wattage is the headlight?

If you are running a 100w unit, that's likely the cause of your issue.

I don't have the specs on the GS850 headlights, but most Suzuki headlights of that vintage were 60w/55 or very similar.

[ThrottleBack]

Slightly off the topic but isn't a 1500RPM idle very high?

[Redman]

On GSes with a headlight off-on switch; the switch is really two switches, 1) to swtich the headlight off-on, and 2) to swtich off-on one phase of the stator. I wonder if the headlight swtich is not switching on that one phase.
Maybe could measure the 3 leads at the R/R, to see if have same between each pair of two leads.



Also, maybe the stator just fails under the more load of the headlight.


And, as mentioned above, headlight isn't more than 60watt is it?

.

[spacepirates]

The headlight should just be stock/OEM. I haven't changed it since I bought the bike, so I can't say for sure, but I'll double check. It'd be nice if the bulb was all I had to change...

a 1500 rpm idle is high. I had it set there for the test, normally I run 1000 - 1100 rpm.

Tuesday evening I should have time to run the full stator papers' tests with both the headlight on and headlight off, and to check the wattage of the bulb.

[BassCliff]

Hi,

Slightly off the topic but isn't a 1500RPM idle very high?

It's a little higher than I like. The factory spec is usually 1050 rpm plus or minus 100 rpm.

For Mr. spacepirates:

You need to clean EVERY electrical connection and ground on the entire bike. When, if, or even if you don't replace the r/r unit, be sure to run the ground wire directly to the negative terminal of the battery.

Stator Papers (Read all sections)

More On The Stator Papers

GS Charging System Health+Quick Test

Stator Test

Stator Replacement

Regulator/Rectifier Replacement

And finally: READ ME!

Then click on my little website.

Thank you for your indulgence,

BassCliff

[koolaid_kid]

Just to mention, a 100 Watt bulb is illegal, but sold as an "off-road" item.

[tkent02]

Sure does light up the local deer population at night though!

[koolaid_kid]

Sure does light up the local deer population at night though!

Yeah, so they can see you better so they can jump right in front of you.

[spacepirates]

Bulb is a GE H6014, a 60/50 bulb.

I ran through the stator papers with the headlight OFF and got good values for everything (save the R/R test part, but I'm running a FH011AA r/r so I don't expect the tests would be the same).

Ran out of time to run through the wiring, but I don't really know what I'd be looking for anyhow. Shorts somewhere? Lots of resistance somewhere else?

[koolaid_kid]

It would not be a short, that would just burn out a fuse and/or melt a wire. I would look for melted connectors, especially in the headlight shell, and a voltage drop across either the headlight switch or the key switch.

[spacepirates]

It would not be a short, that would just burn out a fuse and/or melt a wire. I would look for melted connectors, especially in the headlight shell, and a voltage drop across either the headlight switch or the key switch.

Most of the connector sheaths are yellowed and dirty, so I'll try to more thoroughly examine them as well as check for excessive resistance/voltage drop across connectors and switches.

I might temporarily bypass the switch, too, and run the stator wire directly to the r/r.

[allojohn]

Most of the connector sheaths are yellowed and dirty, so I'll try to more thoroughly examine them as well as check for excessive resistance/voltage drop across connectors and switches.

I might temporarily bypass the switch, too, and run the stator wire directly to the r/r.

You should bypass the switch permanently. It's one of the must do's with these machines.