Battery charging

LR, yours is solid state. It is the aluminium box with fins on it, under the left trim piece. And as the manual says, it is both the rectifier and voltage regulator in one unit. Mine is 7 wires. Black, 3x White, Red, Green, and Brown.
Thanks. I may yet be able to avoid ever having to remove my seat. Next time the temp goes above freezing, I will venture out into my "shop" and take off the left trim piece and see if what I have is original and according to the book.
(Glad it is not the funny little box with wires next to the battery under the right trim piece)
I Crimped and soldiered (is that a word) Green to green, the Blue pigtail to the Bikes Brown, then one of the screws that I used to secure the regulator, I attached a ground wire, and included that into the wiring harness. that was Black to Black. I tried to keep it simple.
Simple eh? :laugh:
If this doesn't PROVE Einstein's theory, it certainly does illustrate RELATIVITY. When it comes to lightning in copper tubes, one man's "simple" is another man's .... well, let's just say it can keep another man LHAO - :laughing:
And keep him "soldiering on".

Anyway, while I may not find any of this simple, I do think I might understand better - so that's a huge step. If I am lucky, I will be able to swap in a unit and stop boiling the battery water and the understanding will be a nice bonus.
I really appreciated all the help. Will post photos of what I find, even if I don't have to remove the seat. Maybe I will do that anyway - just to see what's under there :wink2:
Some bikes I heard came with a tool kit under those seats, I think my wife kept her owners manual there I suppose you may be lucky :) ;)
I Just want to clarified something. The Red wire from Rectifier goes to positive port on the battery and the black goes to the negative port on the battery NOT the frame. Correct?
I Just want to clarified something. The Red wire from Rectifier goes to positive port on the battery and the black goes to the negative port on the battery NOT the frame. Correct?

Yes. To follow the flow. Energy is made in the stator/AC generator. That creates AC alternating current, on the white wires. The white wires go to the Rectifier. The Red wire goes from the Rectifier to the a line that is connect to the batter, and then goes to the fuses.

The negative side of energy, aka the return path. is a neg on the black line. The black line is grounded in 3 spots I can think of. Battery post neg, same line on the engine, and then next to the battery, under the seat its under post there too. Make sure all 3 spots have fresh clean, not corroded connections for the best ground.
black goes to the negative port on the battery NOT the frame. Correct?
Not entirely true. Keep with me, The black wire gets to the battery, eventually. The Wire harness grounds out at the post under the seat. Then the frame becomes a negative pathway for the return power, which ends up going though the engine, to the ground strap, to the battery negative post. Notice there should only be one connection on that post. (neg post)

(I didn't mention the turn signals, they just ground out at their respective site.)

Did that answer your question? I couldn't answer this at work,just cause I needed to verify the wire diagram. The wire diagram is that for the 81 SH model. Good luck


  • Recifier_diagram.png
    188 KB · Views: 346
kinda. I'v rewired my entire bike (cafe style with Estart) and I went out for the first test ride with the new wiring this weekend and my battery died on me (my battery is brand new and had a full charge) I got to found out the hard way that my battery isn't getting charged from the alternator/Rectifier. hahaha I'm hoping the problem lies with the rectifier. As of now my rectifier is grounded only to the frame but is also really old to and not is the best condition thats why I'm wondering if I should have grounded my Rectifier to the battery and not just the frame. I'm going to order a new one soon when I have the money.

The way I have grounded my bike is the battery is grounded to the engine(with thick ground wire), E-start grounded to engine (with thick ground wire), Voltage regulator grounded to Battery, had light, signals and rectifier grounded to the frame. All have the own ground wire. I know it is over kill but it just made wiring that much easier.
Last edited:
The typical reason for the battery not charging, is a failure. In the manual is the test for three main things we just talked about. There is a fourth thing. I uploaded two check procedures. (this is for the SOHC type of bike) obviously I must have made this some time ago, but it was handy.

Here is what I think your problem is. The wire. Go though the manual, and do a Wire check of your stator. The stator to the wiring harness has 2 blocks/white connectors. Check continuty to the stator, write down the numbers. You only need to do the connector cloest to the stator. on the left side of the bike, under seat, near left side of battery tray. 3 white wires. In fact use the google search for 3 white wires. after doing that. Feel the wires. this is my bet. I bet you, that your stator wires are Shot. When you go to feel the wires, you will find (my bet) wire that is brittle, and cracking as you touch it. The bad spot for our bikes is one of the 2 bundles coming out from under the drive sprocket. that wire will be shot right there. And if that wire is shot there, your Voltage reg is shot. Drewpies Re-Wire program from the TECH section list ontop of this page. pic of worn out wires. its my thread, but I think I found a pic that similiar to mine. I thought my wires being shot was 5 inches from the stator. Right where the wire comes down from the Drive spocket cover, and then it bends up, to the first connector. another 12 inches away from that point. At that corner is where I think its shot. Review the threads. It is easy to do this repair job.


  • x400oldRecifier.jpg
    116.9 KB · Views: 257
  • x400oldVoltageRegulator.jpg
    181.7 KB · Views: 269
On most builds people use the frame as a ground path. In most stock harnesses the battery negative cable hooks to a place on the frame. Now anything you install just needs a ground hooked to the frame.
The engine itself grounds to the frame through the engine mounts. I like to have all the engine to mount and mount to frame have bare clean metal to metal contact. This will ensure a good ground path for the ignition. It also ensures a good ground path for the starter.
The starter gets power from the battery on a cable, To ground it does so through it's mount to the engine, engine to frame, frame to battery. Adding an extra ground cable from one of the starter mount bolts to the battery negative has less contact point to fail.
When I rewired my bike this winter, I brought all the wiring harness grounds to a stud on my electrical panel. The stud is connected directly to the battery negative terminal with a 12ga wire. I also have a heavy ground cable from the block to the battery negative that was stock on Maxim's. The fame is grounded to the engine by the engine mounting bolts, but nothing is grounded to the frame.

I went with more and heavier gauge wire than required as I don't want any electrical problems. It isn't a race bike, it is a daily rider. Reliability is paramount!
Thanks for that, I am about to touch up the bike, I will need to remember that. ensure that there is a ground spot, not covered in paint. Thanks again.
Hopefully it will be warm enough to paint tomorrow!
ok here's an update. I can't seem to find any wiring diagrams (in my haynes book) that show you that your Rectifier need to grounded to the battier they all show it grounded to the frame and the red wire to the Battery, witch is what I have done. I checked the Rectifier and its good volts flow threw it. Also I looked at wiring diagram and the pathways for the Volt Regulator and it doesn't hook up to any where to the battery either the volts regulator just runs the lights and is grounded to the frame. So my wiring is looking to be find on that end to. its looking to be more and more a stator problem.
:hijack: I'm also having a similar problem with my votage regulator/charging system. I have an 82 SOHC and I replaced my regulator with the o'reily VR125 with the pigtail. I connected green to green, brown to blue, and black to the regulator case (which I checked for grounding with my volt meter). All of this was soldered. No luck with the voltage. Stator wires check out and I get megnetism on the case when the key is on. However, I used a tiny metal e-clip up against the case to check the coil and it would only stick when it was near a bolt hole. From other places I've read, it seems like it should stick harder than that but nobody has really put it on a scale of 1 to 10 so I don't really know. Does this seem right to anyone or do you think I need to replace the coil wiring?
On the rectifier you have three wires that hook to the stator, these are AC voltages coming in. The rectifier converts these AC voltages to DC. These DC wires, one positive one negative. The positive runs to the battery positive, It may go through a fuse, but it goes to the battery positive.
The negative goes to battery negative. It may use the frame as a path way but it has to get back to the battery.
On the regulator it senses the battery voltage on the brown wire, If low it turns on the power flow through the field coil. This makes the stator put out power. It has nothing to do with the lights.
On the magnetism test you are check the strength of the field coil. If it appears weak check the ohm reading of the field coil. If low it won't create a strong magnetic field.
In checking the rectifier you don't test any voltage, you test the ohms through it. One way then reversed. A rectifier is a series of diodes. A diode is a one way valve for electricity. Checking the ohms one way you should get a low ohm reading, the other a high ohm reading.
Your repair manual should have the test procedure in it.
When I checked my rectifier using resistance meter, it didn't work right. But when I watched the youtube video, there was a special setting on the volt meter to test diodes. That setting worked like a charm. Just an FYI to others.
if the regulator has nothing to do with the light than why on the wiring diagram is the brown wire from the regulator connected to the lights?
Green wire energizes the field coil, Brown wire is a sensor wire. it senses the voltage overage/underage, and sends power to the field coil as necessary. Black might also be part of the sensor. The fuse that the brown wire is attached to is marked Signal. Which looks like it connects to the field coild too, and the main power switch (on/off/on) assuming your looking at the 81 400SH diagram.
The brown wire sends power to most of the bike. As mentioned the reg read the battery voltage off the brown wire. The brown wire also send power to your field coil.
When the reg senses low voltage it grounds the green wire from the field coil. This current flow through the field coil creates the magnetism needed by the rotor to excite the stator into producing electricity.
The reg doesn't send any power out on the brown wire.
I'm getting ready to tackle this myself. Bike runs great until battery runs dead. By skimming through this thread (thanks) I'm going to change the regulator first? The bike is a 78 xs400, so I'm assuming I can use the orielly one that arfstrom used and it will work on my bike? I'm lost in electrical....

This person has a bike that is a year closer to yours. He recommended a Napa Model. I will let you look at his thread, I don't know if there is s a difference between the Napa model and mine. I do whole heartly recommend the pigtails. If like the orielly model, It would be alot of xtra work, you don't need to do, if a 2 dollar pigtail fixes the connectivivty for theReg. in other words look at it before leaving the store. and know you can do it!