Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums > Technical Forum > Electrical > Simple charging system troubleshooting.
So you think you have a bad Stator or R/R ?
I am here to try to make things simple for everybody.I believe in the KISS theory,Keep It Simple Stupid !
Ok, the first thing that Has to Happen is your Stator needs to have the proper AC out put,Yes AC.Set your Meter to Ohms 1k or less.Find the bullet connectors coming from the Stator to the R/R.They are probably burned looking or nasty or both.Unplug all three,don't worry it makes no difference how you plug them back up or solder them together.More on that later.
Check from each of these leads ,coming from the stator out of the engine, One at a time to the engine case.Your readings should be Infinity(OL) or very high resistance,If it is enough to make you continuity alarm ring we might have a problem ,maybe not. Some meters are much more sensitive than others.If it shows no continuity, between each leg(Yellow wire) from the stator it has passed the first hurdle for sure,your stator is not grounded to frame.
Next set your meter to VAC,200 or less.Remember I mentioned AC output,we are now going to test that.Start the bike ( you should have the battery fully charged before testing your charging system BTW) warm up the engine to normal operating temperature. This next part is easier with a helper,but you can do it by yourself.run the engine up to around 3K RPM's and check between any and all combinations of the three leads from the stator,you should have between 40 to 70 VAC .Is the voltage up to snuff ? It may be a little more but it's doubtful unless you have one that has been rewound as heavy duty or high output.Did it pass the test?In order to pass it must have proper voltage between all combinations of A1,A2 and A3,if one combination is very low or no voltage at all you have a bad stator.If it is good ,time to move on.
If it passed the voltage test ,shut down your engine and perform the resistance test you did before you started the engine.Has any thing changed between each stator leg and the engine case? Is it still showing OL or a really high resistance reading?If so your stator is good.Feel very relieved about now.
If not it and it is showing a low resistance reading to the engine ground this is not good,Your stator is probably going to ground when warm.
Is every thing up to par so far.If so your life just got easier.Plug your stator back up or cut those nasty bullet connectors off and solder those wires together and heat shrink them so you don't have to worry about a loose or weak connection there any more.I will note there are some folks who put fuses in those connections.I personally don't like that Idea but its your bike,If they are fused and something down stream from there grounds it can take out one of those fuses and you are running on two legs of a three phase system and loading them even more,which raises the heat in the stator and I believe it can lead to stator failure,JMO ,do what you want.
Now,we are ready to move on,to checking the R/R out put.Time to go to the DC scale on your meter.You do have the seat off don't you? If not take it off now.Check Battery Voltage directly on the battery posts.If your battery is good and charged it should read close to 13 volts.Contrary to popular belief a a 12 V battery that reads 12 VDC is Dead! Charge it up it should read 12.6 or above when fully charged at rest.If it won't charge up or won't hold charge overnight ,you just found your problem.If it needs charging take it out of the bike or at least unhook it from the bike's electrical system to isolate it and test while disconnected.if you have to charge it.Go in the house and do whatever it is you do while not riding and come back later and test the battery voltage.Is it good? Reconnect it.
Now start your bike and warm it up again if you had to let it sit long enough to cool off.Check battery voltage at idle.It may be the same as before or a little less, most unmodified VN7XX's don't charge much if any at idle.with your leads attached to the battery posts run the engine up to around three K rpm's again.At this rpm the charging system should be putting out around 13.6 VDC or so.Are you getting this much voltage.I hope so and your charging system is doing what is supposed to,If not lets move on.
A common problem is a bad connection on the R/R plug.Now it gets fun,if you haven't relocated your R/R it is underneath the battery box and directly over the Goats Belly,so take your left side cover off and see if you can see it.Unplug it and check the terminals on the R/R and its plug on the wiring harness.Check closely,if they are corroded clean them up and I mean, shiny and clean,both sides of the connections.If you cleaned them up good put a little dielectric grease on them and reconnect it.Back to the battery and your voltages.Check them again just like you did before and and see if they are the same .If they are you have a bad R/R or wiring issues and it is time to check the wiring and connections including all the frame and engine grounds,I'll let you go through all that mess alone,you're gonna be a while.
Did the voltage come up to the magic 13+ when revved up ?You fixed it!!! Now go ride!!!
If not start checking the connections and if you clean all the connections and see no improvements It is R/R time.
It is that simple,you can test the R/R values found in the repair manual or in the online manual on here.Let me stress that the R/R readings can be within range and it may still not charge.This why I tell you to check ALL connections before you buy a R/R,it is worth your time even if this not the problem even if you find a bad connection on the R/R .You will enjoy a lot more trouble free miles of riding.
I hope this helps simplify trouble shooting your charging system.I am a firm believer in "start at the start". It all starts with the stator and if it isn't right,the rest doesn't matter.So by all means Check it and the Connectors coming from it FIRST!!! It may save you a bunch of time and grief.
I know this a long post but I would imagine you can do these tests faster than I typed this.
Last edited by denny6006; 02-15-2013 at 02:28 PM.
In order to pass it must have proper voltage between all combinations of A1,A2 and A3,if one combination is very low or no voltage at all you have a bad stator.If it is good ,time to move on.
Last edited by WilliamTech; 02-15-2013 at 02:49 PM.
Everybody who can help keep this simple chime in.Good catch William and I was sure I had missed something.
Denny, Great post. I would like to add an additional comment. Most owners with poor voltage output immediately think they have a problem with either the stator, rectifier, or poor connections. I believe, after working on three bikes, that the headlight relay is the major culprit. If a bike is showing 12.4 to 12.6 volts output ( with a good test on stator and rectifier ), just by bypassing the headlight relay the output will jump to 13.2 to 13.4 volts around 2000 rpms. The relay system really cuts down voltage to the battery.
Very simple post easy to follow.
1988 VN750 - Fixing up for my son!
come on when you turn on the key, instead of when the engine starts.
headlight comes on. Let us know if you have any problems.
Thanks to denny6006 for pointing me to this thread.
As someone who is a complete newb when it comes to anything mechanical related, photos of what you are talking about would help tremendously.
For example: "Find the bullet connectors coming from the Stator to the R/R."
I have no idea where these are, which side of the bike they are on, nor what they look like. See? Clueless newbie!