83GS750ES - Charging circuit

[salty_monk]

My friends bike is overcharging... it wouldn't start - checked it & the battery was pretty much dry!

At idle it goes to about 13v but as the revs increase it goes up & will hit 15-16v (although it doesn't seem to do it all the time - just most of it).

Before you ask there is no extra ground between the RR & battery.

My own 750ES (same bike) displays similar symptoms (though it doesn't go that high & I presumed it was from running with no headlight on it - just testing so that may not be the same symptoms)

So my thinking:

1. The RR is shot
2. The RR has a "sense" wire similar to the Honda & it's not seeing 12v.

Any other thoughts?

Anyone know the charging circuit on these bikes, is there a sense wire?

Cheers,

Dan

[Steve]

On stock GS regulators, there is no sense wire.

First thing to do is to get some water into the battery, However, if it has been run like that for a while, he would be better off just getting a new battery.
Then test it to see what you get.

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[salty_monk]

Sorry should have said... Battery was refilled & charged till full before being put back on the bike. Holding at 12v+ so far.

The other testing detailed above was done after that.

I know there is normally not a sense wire but the 83750ES is a bit of an oddball compared to most GS's in a lot of respects (Mono shock, 16" front wheel, electronic tach etc) so I thought it's possible it might have the extra wire... plan to count wires on the one in my Garage shortly.

Cheers,

Dan

[psyguy]

if the battery went completely dry even though it might still be ok (for a while anyway), for the testing purposes i would buy a new battery so you get reliable data when testing charging

[salty_monk]

I have a spare I can drop in there if necessary... I didn't refill it so I don't know exactly how dry it was. It's not that old, less than a year. Yuasa.

Checked on my bike, no sense wire. Wonder if the RR is screwed then. Better give Duanage a shout if so!

Dan

[Redman]

You asked for any other thoughts:
My thoughts are:
- Yes, could be bad R/R.
- Or, more likley could be a good R/R, but not well grounded.
- Or could, maybe, be that previously had a r/r fail and that failure burnt up the ground wiring, and now have replaced the r/r with a good r/r and is now overchargeing because the ground wiring is burnt up.


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[Redman]

....

And here is the longer explanation and discusssion :

Yes, stock Suzuki r/r does not have sense wire. Good that you understand that.

ANd, yes, on those others that do have a sence wire; if you were to disconnect the sence wire the R/R would then "see" very low voltage (zero volts) and then the R/R whould put out max voltage trying to bring up the sence voltage. Good that you understand that.

But... if the stock Suzuki R/R were to loose its ground wire (or whatever ground connection back to batt neg) it will then put out full voltage (*).
So check to see if the R/R ground (black) wire is no longer connected or has a bad connection. The r/r ground (black) wire is often not in the same little harness as the other 4 wires (stator,stator,stator, output), so to find where it si connected, have to start at the r/r itself. The R/R ground wire is typically connected to a mounting bolt of the starter soleneoid on the battery box (on 850G and 1100G anyway). And even if that wire is connected there, and the connection is good, there still could be a problem in that the battery box itself may not be well grounded to the frame. SHould also be a ground wire (blk/wht) comming from the frame up under the seat up by top of battery box (on 850G and 1100G anyway) thru the main wiring harness down and around to the battery box area and then connected to the battery box (maybe at same place the r/r ground wire is landed). See if you can find both those ground connections and clean them up.

Anyway, that grounding of the battery box is often not so good for various reasons. THis is one reason folks will recommend that you run your own extra ground wire from the R/R ground (add another lug to where the r/r black wire is landed) directly to the batt neg. And this is why the stator papers has you check voltage difference from the r/r black wire to the battery negitive.

So even if the R/R itself is good, it will put out full voltage like you described if it doesnt have a good ground.

Other discussion, not directly related to your present situation, but related to the R/R ground wiring in general, is: Sometimes when the R/R does fail (depending on in what manner it fails) it can burn up that ground wiring thru the wiring harness (other reason to add own ground wire, so doesnt melt other adjacetn wires in wiring harness). I have seen it melt the black/white wire right off of the frame ther under the seat. Melted - gone. And then any replacement R/R may not have a good ground, and then overcharge like you have described.

That is a long description/explanation that I think you will understand (being the SuperStar that you are.)

The short story (no pun intended) would be:
- Check the R/R ground (black) connection to battery box.
- Check ground wire (blk/wht) connections of wire comming from wire harness to battery box.
- Check gorind wire (blk/wht) connection of wire from wiring harness that is grounded to frame.
- And maybe add your own ground wire from r/r ground to batt neg.

And, yes, the overcharging will cause the battery to "go dry" like you described.


* somewhat similar to loosing the sence wire (if had a sence wire), but not so much for same reason. But that is a different discussion.

[Nessism]

Hey Dan,

Make sure the R/R gound is solid/clean to the frame and then make an extension to run it over to the battery. If the bike is still overcharging the R/R is shot. I have a couple of spares you can play with, the one from my 1000 is pretty good sized - much larger than the typical mini sized units Suzuki used. Let me know how I can help.

[Clone]

[

So my thinking:

1. The RR is shot
2. The RR has a "sense" wire similar to the Honda & it's not seeing 12v.

Now, get a new battery, get a ground from the rr to the battery, actually run the ground straight to the battery,and the positive straight to the battery. Then get yourself a relay that gets energized when you turn on the key, hook the one side to the positive post on the battery, and the sense to the energized side, then you should be able to see if the rr is ok. if not then the rr is toast.

[Nessism]

The bike in question is my old 750, the one linked in my signature. The bike is stock. I brought it out of long terms storage but shame on me, apparently I forgot to take care of the R/R grounding. Hope my forgetfulness didn't toast the battery.

[salty_monk]

Ed,

No need to feel bad... The setup on this bike is a little different & that's probably what changed things.

The RR on 750ES Has a 5 pin flat plug that plugs directly into the RR. All the wires disappear back into the loom, none of them are grounded to the frame/battery box or anywhere else easy to get an extra fixing to. There are two ground wires terminating into the same loop for the battery on this bike, I suspect one is the ground for the RR but can't tell without opening up the loom to take a look which I don't want to do.

Redman - With my "susperstar" status I am aware of the issues - actually had them on my G but the oppsite - lack of charging & fitting the extra grounds described sorted it out. Both my own 1000's have extra grounds. I didn't realise lack of good ground could also cause overcharging so your lengthy explanation was great - thanks. I assumed (obviously in error) that overcharging would mean that the ground was actually good - electronics are not my strong box where "black boxes" like the RR are involved.

I'll clean up the connections on the plug & splice an extra wire in to go direct to battery to be sure. How about also grounding the body out of the RR some way as well as the splice to the wire from the plug (using the bolt fixing for the body) would that also be a good precaution or make no difference on this model RR?

Cheers,

Dan

[Redman]

..
...

....
How about also grounding the body out of the RR some way as well as the splice to the wire from the plug (using the bolt fixing for the body) would that also be a good precaution or make no difference on this model RR?

Cheers,

Dan

Dan Mr Monk,

Oh, I quess I didnt know that the charging system wiring on the ES was any differernt than all others. (I though only difference between all/any GSes were some had individual bullet connectors and other had the connector blocks, and prior to 80 had smaller stators.) You are saying the ES is differerent in that there doesnt seem to be any connectors nearby, including the r/r ground (black) wire apparently. Okay, good that we understand that. And then the specific location /method I mentioned about this conenction being here and that connection being there does not apply to your ES.

About grounding the R/R body: I do not exactly recall, but I think I did once notice that the body of a stock Suzuki r/r was not electrically connected to the black wire. I do not have a Suzuki stock r/r on hand to verify that. Maybe someone else can verify that.

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[salty_monk]

I'll take some pictures of the setup on this one so you can better see what I'm going on about....

I think if I splice into the wire just back of the plug, clean all the connections up where the plug meets the RR & also tie the ground into the stator body that will definitely mean it has a good ground...

Dan