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No charging though everything tests great (and has been replaced)

9K views 73 replies 7 participants last post by  thtanner 
#1 ·
I'm about to rip out my wiring harness and replace it. This is getting crazy.

I get barely any charging right now, yet every individual piece tests fine, or better than fine.

Replaced
  • JB (I had a spare)
  • MOSFET R/R (I also had a spare)
  • TPE Stator (just in case, plus I can re-use the other one in my second VN)
  • Battery (last ditch effort since everything else was fine.)

Tests:
  • MOSFET R/R - tests fine. Puts out 15v when unplugged from the bikes electrics.
  • TPE Stator - 20-60vac all legs, zero continuity to ground.
  • Headlight Relay Bypass (no change)

The bike gets 12.5-13.3v, never more. Barely increases with RPM, though stator is definitely pushing out vac. I was getting as low as 9v @ the ignition coils with the fan running, so I did the ignition coil mod. Now I get battery voltage at coils (runs better now, no longer dies when the fan kicks on due to low voltage).

MOSFET bypasses stock wiring harness (direct to battery, 30a inline fuse). Replaced the switching style inline fuse with a standard type, no change.

I am thinking there has to be some sort of short somewhere causing this issue. I can't think of any other reason why my voltage would be so low. I have 2 spare harnesses, so I guess it may be prudent to swap it out as I can not see anything that would cause this.

Any thoughts? Am I missing something stupid? I mean I've seen 100s of VNs diagnosed here and I swear I've covered all the bases.
 
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#2 ·
Is the headlight relay sense wire supposed to have any continuity to ground? It does, no matter what JB.
 
#3 ·
Have you tried moving the harness while
Testing everything? I had a burned wire that was arching out but only every so often. Everything tested fine on my bike as well.
 
#4 ·
as mentioned, look for a short (or otherwise a very high electrical load of not a direct short).

if the RR is putting out good voltage level with minimal load (un hooked), put the output drops when hooked up, either a very heavy load exists which is pulling down the voltage by 'overloading' the charging system, or their is a bad connection or failing RR.

the heavy load will cause voltage drop due to the amount of current (amps) avail from the stator being insufficient for the regulator to keep the output voltage up.

bad connection will cause the voltage at the battery to be less than what the RR is thinking the battery has (voltage drop across the wiring/connections).

try checking the voltage right at the RR when connected if possible (many multimeters have leads with sharp enough points to be able to pierce insulation for this type of measurement).

also, ground connections can affect the output voltage when under load, so don't look just at the positive side of the system.

the headlight relay does appear to be grounded thru the starter solenoid. the trigger wire from stator has a diode in it, but does end up grounding thru the solenoid.
 
#5 · (Edited)
My system gained 1v when I bypassed the start circuit from the JB. Seems to be a common fault in the JB, and a possible source of stator failures. Ever have any trouble with the start button? I also have the headlight relay bypass in use.

I could try to dig up the post if you're interested, you can test it before cutting any wires. MTB has done the same bypass. Before the bypass, the new system topped out at 13.5 and would brown out to 12.5 or so, it's a solid 14.5 now except when the fan is running.

20v AC seems a bit low, did that leg happen to be on the headlight relay? I'd bypass the start circuit and headlight relay if so.
 
#6 ·
20v AC seems a bit low, did that leg happen to be on the headlight relay? I'd bypass the start circuit and headlight relay if so.
Stator was disconnected from wiring harness (and headlight relay). All legs produced the same voltage (20vac 1k rpm, 60vac+ at 5k rpm).

try checking the voltage right at the RR when connected if possible (many multimeters have leads with sharp enough points to be able to pierce insulation for this type of measurement).

also, ground connections can affect the output voltage when under load, so don't look just at the positive side of the system.
The R/R bypasses the stock wiring harness. Voltage is the same @ the r/r connector as the terminals on the battery when connected.

I did triple check grounds, just in case. No dice there either.

I have also jiggled wiring with no success, but it's tight against the frame in places and that's where i'm imaging the issue lies..

I'm really leaning towards a short as there isn't much else that can put that kind of load without being a major issue. I'll probably just pop the tank off in an hour or two, put in a spare harness, and go from there.

Who knew a 30 year old bike would have wiring gremlins. ;)
 
#7 ·
Ok, sounds like stator output is ok.

The short .... could still be that circuit in the JB, even both the JBs you tried.

If you wanted to try the bypass as a test, you could simply pull the correct wires from the 10-pin plug on the JB, tie them together and start the bike. Then check the charge voltage.
 
#8 ·
At this point, it can't hurt to try. It'd be crazy if two JBs were bad, but definitely not impossible. I do have a third to try, too. (I've been stockpiling, I had two VNs here - about to start on the second was just trying to 'finish' this one)
 
#9 ·
We see a lot of wonky JBs here. Searching for my thread on the bypass, there are a lot of posts about this start button problem and dead shorts in JB. I've seen enough to think this is a significant bypass to do, even as a preventative measure.

Link to the thread where I fixed mine:
http://www.vn750.com/forum/19-electrical/69625-start-button-wont-work.html

The bypass:

The Fix: Clipped two wires off the 10-pin JB plug: black/ red and yellow/red, spliced these two together.
Note: This bypass also disables the nanny switches on the sidestand and clutch.

I think there's just too much BS occurring in the JB. :)
 
#10 ·
I'm throwing in a new harness in a minute, and if problem persists, I will then try that mod. I don't mind the safety switches, but if that's the issue then I'm more than happy to disable them :D
 
#11 ·
Wiring harness pulled. About to put the new one in. Going to swap the battery box (mine is really eroded from old batteries) and all associated electrics (from an 05? I think).

 
#12 ·
I am having way too much fun tearing the bike down right now. Going to use the opportunity to clean in various spaces that are hard to get to normally.
 
#13 · (Edited)
I ran into 2 connectors that have less wires than the original 86 harness.

1: 4 wire from dash cluster has 2 wire connector on new harness

2: 6 wire connector from horn/turn signals/etc only has 3 wires on new harness. I'm guessing this is the self canceling blinker delete.

Any feedback to what cable goes to what?

Edit: If anyone runs into this, the top portion of the 2 connectors is related to the auto-canceling turn-signal unit that was deleted in 89. For the 4 pinner, just match the colors and it will be the bottom portion of the plug (file a little off the connector to allow it to connect). Do the same for the 6 pin, using the bottom row of pins to connect the connector. It becomes fairly obvious as you look at it what is what. The 6 pin (which is now a 3 pin) is the clutch safety switch.
 

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#14 ·
Figured it out.

In short, use the bottom part of the connectors. The bike is up and running....

With very little to no charging like before. I'm at a loss since everything works until its on the bike. The only components that have not been swapped are the dash, that's about it.

Going to try the safety switch bypass to see if one of the safety switches is the culprit. I'm out of energy for today, though.
 
#15 ·
Follow-up: Could a bad ignition coil cause abnormal draw? That is one of the (few) things that have not been changed. I have a spare set, so may be worth swapping just for kicks if the safety switch bypass fails to help.
 
#16 · (Edited)
Hmm.. I am able to find multiple occurrences of this type of problem. They're similar in nature.

http://www.vn750.com/forum/19-electrical/34618-issues.html
He had a ****ty meter so who knows . I do know for sure my stator is *not* grounding at all. I have a Fluke 110 and it has not failed me yet.

http://www.vn750.com/forum/19-elect...tator-wire-grounded-through-junction-box.html
Curious if this is also related.

I am just dumbfounded, so it's time to get systematic. I'll disable the kickstand and clutch safety switch's individually (manual bypass) and test. From there, doing the full bypass per Spockster. I'll just go down the line until I find it. At least I know the wiring harness is good end to end now. I have a few more JBs to play with too for kicks. Heck, the ignition coils will be swapped for fun.

Heck I'll also unplug the tach and see if that's it. They have had shorts in them before...
 
#17 ·
I would have tried Spockster's bypass first,as that's easier than a full rewire,but that's just me.I tend to listen to people who've fixed the problem I am having.;)
 
#18 ·
It's not technically a fix, but a work-around. If it 'fixes' it, then I'll track down the root cause. I still am not convinced it's 100% either as his idle voltage isn't 14v; with a mosfet it should be.

That aside, I found so many issues with my harness I had been wanting to pull the new one anyways.
 
#19 ·
I can understand that,was just pullin yer chain a little. besides it is an experience you've gained.when I put my 85 motor into my 86 I didn't realize how bad the harness was on the 86 and wished I'd changed it before I put in the motor.as far as the harnesses I've done on bikes though,these aren't too bad
 
#20 ·
It could have been a lot worse to be honest. Remove tank, few other bits and bobs.. pretty strait forward. Took some common sense thinking for the auto canceling signal delete, but all good there. Fired up really eagerly.

Now it's just the principle of the thing. I'm just damned curious to figure out wth! I have a weird feeling I need to disco the tach and see what happens. Weird inkling
 
#21 ·
Doc was reading my mind again.... Just unlock the two spades from the plug hold them together, test. If the test is negative, slip them back into the correct holes ... assuming you noted where they were :) .

Wait .... Why doesn't my bike idle at 14v? Because I think it does now, maybe 14.5. Hell I'd call it a fix, my start button works now, I don't have charging brownouts, and it gained 1v of charge.

Congrats on the harness though, my internet went down late yesterday afternoon. Was going to suggest tracing on a wiring diagram, but I found at least one or two errors in the color diagram, where my harness had different colors than shown.

I pulled my harness just to get the airbox out in one piece, wasn't too bad.
 
#22 ·
I swore the post I read you were getting 13 something afterwards, my bad. Doesn't ever bother you as to why that fix worked? I have no issues with start button etc, but that doesn't mean one of the safety switches isn't grounding out internally causing massive resistance; i'd just like to know which one and replace it if possible. My wife also rides and I'd hope to not have to explain the various safety switches I bypassed if she wanted to take it out.

I also want to check my tach as the front ignition coil feeds it; I can see having a short in there as well. I have had my bike die randomly and I'm thinking it all ties together under one gremlin.
 
#23 · (Edited)
Really just the opposite, I'm thrilled the cure was so easy, at least in my case. Why it worked doesn't really bother me, it's my half-assed assessment that the circuitry in the JB is over-engineered to accommodate the nanny switches and headlight relay, and possibly poorly executed. If you can make something work with a hammer, why hit it with a cruise missile? (referring to the bypass)

The one wire (yellow/red) that branches off the start wire and runs to the IC Ignitor box , seems to be a common theme in a lot of JB failures. (headlight-stator-start circuit-relays-ignition) The circuit in the JB goes to fault, then the chase is on. Having mistakes in wiring diagrams doesn't help at all in trying to understand these problems. I know next to nothing at all about the circuits inside the JB, but I know bypassing that JB is a viable option many times.

I wouldn't rule out a problem in a coil, but I don't think it would be a problem unless the 12v supply to the coil is able to short to ground. We don't have points type ignition, but we have that yellow/red wire that routes through the IC box.

My bike had also cut off randomly over three years, but hasn't since doing the bypass. Also, from day one, I would randomly have to hit the start button 2-3 times to get it to crank, then total failure to crank led me to the bypass, and that cured it. It starts better hot or cold now. And the TPE/MOSFET now produces the 14-14.5v at idle. I had posted previously to Slim that I was getting 13.5v at idle with the new charging system, and last year I was having those brownouts which are also gone after the bypass.

I feel lucky to have not cooked the new stator with this JB problem. I thought of the bypass as a possible cure, then after posting about it, found michiganteddybear had already done the exact same workaround, so I knew to roll with it.

If the bypass happens to work for you, someone should write a clear, concise detail of it, and make it a sticky. It's just too dang easy to do, even as a preventative measure to head off future problems. I will say there was one recent post that showed this bypass didn't help with the voltage. I'd still bet it's in that JB though.
 
#24 ·
Really just the opposite, I'm thrilled the cure was so easy, at least in my case. Why it worked doesn't really bother me, it's my half-assed assessment that the circuitry in the JB is over-engineered to accommodate the nanny switches and headlight relay, and possibly poorly executed. If you can make something work with a hammer, why hit it with a cruise missile? (referring to the bypass)

The one wire (yellow/red) that branches off the start wire and runs to the IC Ignitor box , seems to be a common theme in a lot of JB failures. (headlight-stator-start circuit-relays-ignition) The circuit in the JB goes to fault, then the chase is on. Having mistakes in wiring diagrams doesn't help at all in trying to understand these problems. I know next to nothing at all about the circuits inside the JB, but I know bypassing that JB is a viable option many times.

I wouldn't rule out a problem in a coil, but I don't think it would be a problem unless the 12v supply to the coil is able to short to ground. We don't have points type ignition, but we have that yellow/red wire that routes through the IC box.

My bike had also cut off randomly over three years, but hasn't since doing the bypass. Also, from day one, I would randomly have to hit the start button 2-3 times to get it to crank, then total failure to crank led me to the bypass, and that cured it. It starts better hot or cold now. And the TPE/MOSFET now produces the 14-14.5v at idle. I had posted previously to Slim that I was getting 13.5v at idle with the new charging system, and last year I was having those brownouts which are also gone after the bypass.

I feel lucky to have not cooked the new stator with this JB problem.
Fair enough.

I just wonder if the issue lies within the JB, or actually at one of the saftey switches. I have a total of 3 JBs and there is no difference when they're swapped. They could all have the same issue, but it just seems unlikely.

Either way, I'm going to try the bypass in a few minutes. I'm waiting until 10am as not to annoy the neighborhood constantly running the bike.
 
#25 ·
It would be a trifecta if all three were bad, but the odds are still favorable with the assorted problems we see here about the JB.

Just get a straight pin or stiff wire, find the tabs on the spades, release them from the 10-pin plug, get the two together securely and fire it up with a meter attached to the battery.

Wow, you mean there are places where neighbors are considerate of each other?!! What planet? lol

I hope this bypass works, after all this. If not, I'll have to stop talking about it. :)
 
#27 · (Edited)
and even then you probably wont feel anything... it'll take more than 12-15 volts to give much of a shock thru skin.

Oh, and a correction on the nanny switches, the bypass that KM and I have done will bypass all the switches for starting (clutch, neutral). it does not bypass the run/stop on right bar, and it does not bypass the side stand switch, which isnt used in the start circuit anyway, only to kill ign if you try to ride off with the stand down. yes, it uses the clutch and neutral switch in that circuit, but I had to bypass my side switch (actually removed completely) about 6 months after I did the start bypass.
 
#28 ·
Pictures say it all. My rear cyl is still dropping out, though and bike occasionally dies at idle. Testing the coil, etc.
 

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#31 · (Edited)
Sure looks that way! Is this true THT?

Thanks for keeping me straight on the switches, MTB, I just tend to include all as a disclaimer.

Tanner, find out if that cyl is losing spark or fuel, may have overlapping problems here. Choke it and see if that cyl picks up, or check spark while running.

Probably wouldn't feel full battery amps from those wires, but if you get 12v/220 amps while soaking wet, you will tell everything you know or make something up! We have ways of making people talk! ;)
 
#30 ·
Tested a different igniter, no dice. Trying a different coil real fast..
 
#32 ·
New coil and wires, same issue with rear cyl. Going to check resistance of the pickups make sure there isn't a wiring issue there.
 
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