Jumping Voltages...checking across battery

[BigD_83]

I've never pretended to be a whiz at electrical, and this is a story followed by what I hope is a simple question with a simple enough answer so here goes:

I had been away for a few weeks, and yesterday got out riding for the third or fourth time since I got back. I went to pick up my girlfriend so we could grab some ice cream down by the water, and when we came out to go, the bike wouldn't start. I mean, not even a casual turning over. Later, after enjoying said ice cream courtesy of our Subaru's participation in the evening, I decided to try the 650. This time, it fired up with ALMOST no hesitation.

So we go inside for an hour or two, and when I start it up to go home again, wouldn't you know it...nothing. No solenoid click, no lights dimming, nothing.

After jumping the bike off the (not running) Subaru battery and getting it home, I put the multimeter on the battery, and the DMM is only registering 4.58V when the start button is pressed. No wonder it doesn't want to start!

After a full night's charge on the trickle charger, the bike fires right up. Good thing, as I had an appointment with the road examiner. I put the DMM on it to see what the situation was, and the voltage was jumping around like crazy. I didn't have time for it so keeping all of my fingers and toes crossed for the morning I was able to get gas, make my appointment and get home without the bike dying.

I tried the DMM again with the same result. Changed the batteries on the DMM, same result. Changed the leads, same result.

The odd thing is that the voltage was steady (12.83) when the bike wasn't running, dropping to 12.53 key on. As soon as the bike is fired up, the DMM is jumping around like a 12 year old with fire ants in his underwear.

Note that the only thing I have done to the bike electrically in the last week is replace the lost stock horn with dual tone FIAMM clones (single terminal, ground through mounting post) and the horn relay mod. I checked the stator and R/R last month and all checked out fine

This seems like a ground wire problem to me.

Question: can ANY loose ground wire cause a problem like this or would only a problem in the stator, R/R, and/or battery explain this behaviour?

There, I hope the question is simple enough. I suspect the answers won't be.

EDIT- I removed the fuse from the inline fuse on the horn relay mod, and that didn't change anything. The voltage was still jumping around

[tom203]

Disclaimer: I've not looked at horn relay mod, but....

Very likely horn wiring problem. Stock setup had horn hot with ignition on and activated by grounding out at handlebar button. Disconnect your horn wiring (and relay) and watch DMM

PS; horns don't help much these days- drivers are happily overwhelmed with noise!

[BigD_83]

Thanks Tom,

Pretty good rule of thumb that if things change, then the last thing you did is the likely problem.

I thought that by disabling power to the relay I'd be good, but I should have thought about disabling the power at the switch as well. Now that I have had a better look at the wiring diagram, that switch ground does feed back to the R/R, so I probably have a bad splice in there. Could be why the horn was dodgy in the first place.

http://members.dslextreme.com/users/storagecliff/images/gs650_wiring_diagrams/1982GS650GZ-1983GS650GD.Jpg

In the horn relay mod (like the coil) power from the battery via the in-line fuse is always hot (key on or not). The wires from the horn switch are cut and connected into the relay. There was already some dodgy wiring there from a PO's efforts, at least that is how I interpret the splicing/electrical tape with non-stock wiring colour.

I'll have a look at it tonight.

P.S. there is a new malady out there: instant deafness. Put a cell phone in someone's hand and they instantaneously cannot hear. It is accompanied by instant blindness, and acute loss of intelligence

[spyug]

I had that recently on my 550 and it tracked down to insufficient grounding from the R/R.

Only the ground from the R/R was attached to the battery negative post and the body of the R/R was attached directly to the frame. I added another lead from the R/R lead directly to the frame at another point and made sure the attachment point for the R/R to frame was metal to metal and that sorted the problem for me.

Hope that helps.
Spyug

[Steve]

In the horn relay mod (like the coil) power from the battery via the in-line fuse is always hot (key on or not). The wires from the horn switch are cut and connected into the relay.

Just curious why you cut the wires.

The horn relay is even easier than the coil relay, because all you have to do is remove the wires from the horn(s), connect them to terminals #85 and #86 on the relay. Fused power to #30, #87 to the horn(s). If the horns have two terminals, connect the second terminal to ground.

.

[BigD_83]

Just curious why you cut the wires.

The horn relay is even easier than the coil relay, because all you have to do is remove the wires from the horn(s), connect them to terminals #85 and #86 on the relay. Fused power to #30, #87 to the horn(s). If the horns have two terminals, connect the second terminal to ground.

.

I had to cut and splice in some new wires due to a PO's botched job on the old ones. There were a number of bare spots covered over with electrical tape, from which the glue had started seeping into the bare (not soldered) wires. I took the opportunity to clean up the wiring mess.

In the process, I found a few other dodgy connectors kicking about that I felt compelled to replace. I thought I had done a decent job of cleaning/checking things last year, but it's obvious I didn't have enough experience at that point to recognize some of the obvious signs.

[BigD_83]

I had that recently on my 550 and it tracked down to insufficient grounding from the R/R.

Only the ground from the R/R was attached to the battery negative post and the body of the R/R was attached directly to the frame. I added another lead from the R/R lead directly to the frame at another point and made sure the attachment point for the R/R to frame was metal to metal and that sorted the problem for me.

Hope that helps.
Spyug

Spyug,

I'm not sure I follow what you did to correct the situation.

Is this it?

You have a lead going from R/R to Battery "-" and a second lead from a second location on the RR going to the frame, and R/R grounded directly to the frame?

Or is it that you Teed into the lead going to the battery, and ran a second line from the same R/R source to ground?

[spyug]

Or is it that you Teed into the lead going to the battery, and ran a second line from the same R/R source to ground?

That's what I did.


The jumping voltage really was giving me fits and I had myself convinced my stator was acting up but Steve and Nessim put me right. I should have figured this out myself since its a very common axiom in motorcycle wrenching that a majority of electrical faults can be traced to poor grounds. I've heard it over and over but somehow forgot it this time.


Check your grounds are now the words I live by.


Good luck with you issues,
Spyug

[BigD_83]

That's what I did.


The jumping voltage really was giving me fits and I had myself convinced my stator was acting up but Steve and Nessim put me right. I should have figured this out myself since its a very common axiom in motorcycle wrenching that a majority of electrical faults can be traced to poor grounds. I've heard it over and over but somehow forgot it this time.


Check your grounds are now the words I live by.


Good luck with you issues,
Spyug

Thanks for the clarification.

It sure concerns me that I cannot monitor the charging (or lack thereof) to see if there really is (or is not) an R/R or stator issue. The good news is the battery is accepting a charge now, despite the jumping voltage. However, a loose ground may present some rather unfortunate consequences.

My money is that my monkeying around with the horn switch ground and old wiring is the cause, but I've been meaning to look at the R/R grounds anyhow. That should be good entertainment this evening.

[koolaid_kid]

You can always use the star configuration that posplayr uses. He runs all the grounds to one bolt (IIRC it is a R/R mounting bolt) and then runs a wire from that bolt to the battery negative terminal.

[BigD_83]

You can always use the star configuration that posplayr uses. He runs all the grounds to one bolt (IIRC it is a R/R mounting bolt) and then runs a wire from that bolt to the battery negative terminal.

From what I have seen, that seems to be a very clean and elegant solution.

[tom203]

You can always use the star configuration that posplayr uses. He runs all the grounds to one bolt (IIRC it is a R/R mounting bolt) and then runs a wire from that bolt to the battery negative terminal.

I do this but also add an additional 14 gauge ground wire from there up to the bolt that holds fusebox on.

[BigD_83]

I do this but also add an additional 14 gauge ground wire from there up to the bolt that holds fusebox on.

Tom,

what is the rationale for the extra ground wire to the fuse box? Is it just that it is a convenient location?

[tom203]

Tom,

what is the rationale for the extra ground wire to the fuse box? Is it just that it is a convenient location?

I "feel" it offers a shorter path for ground returns from front stuff, like headlight but it is overkill. The common ground point nicely connects the ignitor and R/R with the jumper to battery. I use the lower bolt that holds ignitor/ regulator plate to airbox (just behind battery box -lower front) as the common grounding point.

[BigD_83]

Having totally removed the horn circuit from the equation, I tried the DMM on the battery yet again. Same result.

I moved the grounds from the R/R to more solid frame points. Problem still exists.

Last night, I ran across this thread from someone experiencing the same symptoms, and resolving the issue with new spark plug leads.

I have brand new Dyna Green coils and new Dyna spark plug wires...surely they couldn't be causing this issue?

One of the things noted in the previous thread was the detection of stray EMF. I had also noticed that as I approached the running motorcycle, the DMM would start going nuts. The closer I got to the coils and spark plug leads, the worse it became. About two feet away from the motorcycle, the jumping readings stopped. There was no problem at all with the key on but the engine not running.

I am now starting to suspect that the new spark plug leads are actually the problem. I'm in the process of reconnecting the old coils and leads to see if the problem goes away. I need to figure out an easy way to connect the small Dyna ring terminals to the male spades on the stock coils