charging system defunct.. Help please.


XS400 Member
Reaction score
santa ana, CA
Im broke and cant afford a mechanic. I want to fix it myself but my knowlege of the electrical and charging system is zero. For a while i have been charging my battery and getting about a week of good use out of my bike. when i notice my lights dim or my electric start wont work i recharge my battery. this routine is working for me but it is getting old fast. I really want to get this fixed but dont know what to do or where to start. Please advise. Thank you in advance.
alright, i checked the service manual under charging system and think i can take it from there but i dont know some of the components that they refer to(pretty much all of them). could anybody please help to familiarize myself with what are the following parts: alternator, rectifier, regulator, field coil, and alternator armature.

thanks again.
We've all been there!

Read my write ups about the stator rewire. You'll learn as you go.

basically your bikes engine runs a power plant (stator/field coil) they rotate and send AC to your regulator rectifier which turns the output from the power plant to DC, battery voltage.

To make sure it doesn't OVERcharge the battery, the regulator dumps the extra voltage once the charging current gets high, around 14.8 volts for some bikes. No or bad regulator means you'll have above 14.8 at revs above 2500 rpms. You can check across the battery terminals with a cheapie voltmeter while the bike runs.

if it's good, you might have other issues. first. test out your output volts for us.

but....sounds like you have an old battery to start with.
Been there, Fixed that. Drewcifier has posted alot, as well as Drewpy, and even Sbondini. I know the info is out there, I have posted my :twocents: fairly frequently. I don't know whos write up I like better, I think I printed Drewpies, and went shoping, then read Drewcifiers many times, prior to doing the job.
Good luck, Tobie
thanks for pointing me in the right direction. ill update as i make progress. i love this website. its good to know that there are other people who have had the same problems here that can help and offer valued input. thanks again.
alright.. so i got my multimeter and am going down the list in the service manual, i just got a couple questions. where is my alternator? and where do i find my field coil/armature?
Alrighty! The Alternator is the projection on the left side of the engine, (as your sitting on the seat.) There is 2 sets of wires going up the on the left side, back of the motor The first connector, goes to the wiring harness. From there it goes over the Air filter, compartment. to the behind the Air filter cover.(rightside of the filter) From there there it connects up to both the rectifier, and the Voltage Regulator (vr) So the first connector is up by the Air box. (infront of the filter) Then it is connected to a jumper, which just goes over the airfilter box. The VR, and Rec are both attached to the Battery box. Screwed on Hella tight. As long as your messing with the connectors, Clean em up, and put some petroleum jelly on the connectors, or dialectic grease. (sand paper first)

Drewpy's (Great Pics) Probably has all the answers all ready here! Just need to varify that its covers your model bike, but the technique looks dead on! Check em out!
Good luck!
Go through the diagnostics before you tear your alternator apart. I have rewired my alternator a per drewpy's write up, but ultimately the real issue was dirty grounds, a "new" battery from the PO that had low amperage from a bad initial charge, and a faulty regulator. Don't get me wrong, its good to know that the wires going to my alternator/stator are new, and yes, it was fun to do that, buti n general, I prefer less variables.

drewcifer and arfstrom, god bless their hearts for always being exited at the proposition of a rewire - we all must remember the KISS rule (keep it simple, stupid)
Hay now, I amstill In diagnostic mode, :rolleyes: Hoping at least to clean up connectors, and apply a little protective grease ;) perhaps find that bad grounding accidentally :smoke: Have Multimeter, start testing. (Great Pics) Probably has all the answers all ready here! Just need to verify that its covers your model bike, but the technique looks dead on! Check em out!

Tombo....tee hee.

You trusted a PO's battery?

All teasing aside since his whole post qualifies as a "tell on yourself"

Simple is usually the cause. Had a dif bike stall out on me while riding last night...after two hours of cussing, saw the petcock vacuum hose detached. What a noob boo boo.

So yeah, try all your simple stuff first. I often assume that's the first thing people do. Funny thing is a failed flasher relay was what led me to my stator failure!

Good luck,and k.i.s.s.

After that, manual, voltmeter, grounds, battery, stator. Not in that order. LOL
:stupid: Okay, I did the same thing, at my first attempt at passing the "road test" the State tester guy did give me a chance to go away, and attempt to fix it, I didn't listen. My petcock vacuum line was off the Carb intake holder. :doh: :hijack:
Back on to topic, yup, take your time, KIS, Examine everything, One thing at a time. Judge each thing on its own merit, and Report back to us, or look up the pics/Especially if you get stuck. Before I was married, my wife drove this bike, had 2 Batteries, so every day she charged the battery, and charge up the dead one. so I had. So I suppose that is a pretty easy fix for some people. So good luck with what every you decide to do.
Funny thing is a failed flasher relay was what led me to my stator failure!

funny you should say that.. i have been having this issue where when i hit my blinker switch it doesnt work the first time, but if i hit the opposite direction first then go all the way across to the direction i want, it usually works about 60% of the time.. is this a sign of a failed flasher? could it really be that simple?
Could be, I have seen posts where its was the switch, If I remember right, it basically disintegrated on the person.

What you are describing is almost assuredly a problem with the switch. The switch can be taken apart and cleaned. The flasher is before the switch in the turn signal circuit so the flasher does not know if you have activated left or right turn signal.
a quick way to test if the magnets are good in the alternator is to hang a box wrench on a long screwdriver....lay the tip of the screwdriver between two of the cooling fins on the motor, and let the wrench dangle about 1/4" away from the lower engine cover on the shifter side (the alternator is under there).....turn your ignition switch ON and see if the magnet draws the wrench to it. if that's what happens, move to testing the regulator and rectifier.
No, In my experience the flasher relay fails when other electrical issues arise, a lot like a fuse by another name.

While I don't remember enjoying finding the bugs on my bike I did enjoy the confidence I gained afterwards.

Good luck.

the signal issue you're having is the same on my bike. Open it up and carefully take it apart. (Over a towel, there are tiny screws and parts.)
Brush it all clean and shiny in there if it's metal. There's a metal slider with a spring loaded ball bearing that locks your signal left or right. it's the track that rides in that rusts up. De rust in a vinegar soak, then brass brush it clean as you can and lube it up before re assembling. Remove all the old dieelectric grease in there and replace with graphite or new grease. Will bog up in the cold in my opinion, grease.
alright.. first, HAPPY NEW YEAR!! yeah.. its new years eve and im playing w/ my bike.. what can i say... we do silly things when were in love right? anyway. i did the magnetic test so that means my alternator is working right? well i did the output check anyway and with my engine running i measured 12.25 across the terminals. because it was low, i moved on to the field coil/armature tests. now heres where i found a little confusion.. it says "check the resistance between the 3 white leads". I found the 3 white wires and disconnected the connecter, then bridged the gap between them wiht my multimeter. i got no results. i tried different pins and still got nothing. tried with the key on/off nothing.. i tried different pin combos on the same end and got nothing any which way. this is why im confused. do i even have the right 3 white wires?
Happy New Year, (possible the 2nd?)

this is a pic from Drewcifers Albulms. it shows the 2 different connectors, and the placements of them. My bike I remember coming up from the stator, back of the engine, up to behind that H Airbox, then connecting to a another connector behind the Air filter box (shown). The 3 white wires go from there to under the battery box. to the rectifer. So with all that said, my memory getting foggy, too much sparkling grape juice, Find the manual, double check the rectifier, unplug both sets, and test them individually. as per manual. Symptoms are awe fully like the the dreaded bad wires syndrome. Make sure the idle gets over 3000rpms prior to lableing it bad. once it hits 2.5k rpms, to 3k, you should be at 14. something volts. (forgotten) Not looking it up, (evil grape juice) Look up the thing about adding volts to the Green wire, just to ensure your getting full amp's to the field coil. Keep at her, she will be running and charging in no time.

Bad Wires