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Help: diagnosing overcharging.

Discussion in 'The Garage' started by DESTROYASAUR, Aug 6, 2017.


    DESTROYASAUR XS650 Enthusiast

    image.jpg Hey folks,
    Been cruising the forum for sometime but this is my first post. Y'all have been a wealth of information and frankly a pleasure to read about. Thanks for that! Now, onto the bike.

    It's an 82 haritage special, stock apart from the bars, the jerker exhaust system, and my upgrading the brakes. It's got about 24,500 miles, and has been running great, albeit a little hot, whenever the charging system doesn't throw a monkey wrench into the works.

    Latest issue is: first I got a new rotor from mikes, the cheep piece of shit not only needed the rare earth magnet mod but after less than 50 miles the screws backed out, causing the glue over the soldered connections and the connections themselves to brake. Suffice to say it wasn't working until I learned from you guys to check for that and was able to solder it back up and throw some locktite on the screws.

    Everything was good when I first got the rotor, now that it's back running suddenly I'm overcharging my battery. I've gone through curlys guide a lot and everything seems to check out, with the acception that the ac voltage between the white wires at the stator plug is reading 9VAC rather that 10.5-11VAC. All subsequent tests in that section check out correctly though, so I'm not sure what to do with that information.

    Personally when I see the voltage rise past 14.5VDC when I rev the engine I expect the regulator to be the issue. However, according to the curlys guide, if the slap test checks out then your regulator is fine. Can someone explain that? I'm not sure how checking that the alternator is creating its magnetic field correctly says anything about the function of the regulator. Anybody got any thoughts?
  2. mrtwowheel

    mrtwowheel Honda Etched On Brain Top Contributor

    Regulators do have different "set points". One regulator may have a set point of 13.5 volts DC, while another regulator may have a set point of over 15 volts or more, and another may have the perfect set point of 14.2 volts. Blaming the regulator "set point" for being too high can only be determined if the wiring that the regulator uses to determine battery voltage is in good shape, without some reason for unnecessary resistance.

    So, if everything else is right, and the charging voltage is high, blame the regulator.


    DESTROYASAUR XS650 Enthusiast

    Thanks for the reply Scott.

    Which wires would I be checking for resistance then? The green, brown, and 3 white wires between the alternator and the reg/rec? Or the brown coming out of the reg/rec and going to the fuses and main switch? Also, what is too much resistance in this case?

    If I keep revving the bike it'll go up to 16 volts DC at the battery. I've avoided pushing it higher than that. Correct me if I'm wrong but that seems like it's much too high even for the "set point" on a regulator.


    DESTROYASAUR XS650 Enthusiast

    Also, it didn't always rev up that high. In the past it's always just gone up to 14 volts DC.
  5. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    just did an A_B comparison of a pair of "original" solid state voltage regulators one had 14.8 as high voltage the other 14.5 luck of the draw or how they age I guess. check all your grounds carefully as well as the hot wires. Where are measuring voltage from? check at a couple of different places; frame, battery neg, engine case, before after fuses.
  6. DanielBlack

    DanielBlack XS650 Junkie

    Sounds to me like the sensing circuit of your regulator might be open or not as clean as you'd like.

    As you point out above, there are some wires going to the alternator and the another ties in to your main switched power. The latter is the sensing circuit, telling the regulator whether to turn the rotor on our off via the brush wires. The three white wires send A/C power to the rectifier and battery.

    When the sensing circuit sees less than the set voltage (~14.2v) it closes the brush circuit, turning the rotor field on. If the sensing circuit is open or dirty the regulator might not ever see the +14 voltage, never turning the alternator off letting charging voltage go through the roof.

    The successful slap test tells you the regulator can open the gate, but not if it can close it.

    DESTROYASAUR XS650 Enthusiast

    image.jpeg image.jpeg image.jpeg Okay, so we have some interesting forward motion. The problem has resolved itself, which is both wonderfull because I get to ride tonight and terrible because I'm not sure what caused it/when it'll be back. That being said, I'm hoping with your help we can figure it out.

    First off, I checked battery voltage at the frame, the the cylinder fins, and even the top of the key switch, and they all read battery voltage. Also, I was checking battery voltage between the battery terminals. That made me feel better. Great thing to check, thank you Gary.

    Next I was looking into the sensing circuit that DB mentioned, and that's when things got interesting. I'd forgotten to mention that I've had a strange problem lately that when I ratteled my fusebox when the bike was ideling sometimes the bike would shut down. Now I looked into it further and with the key turned on but the engine off. when I ratteled the fusebox I could here the relay under the left sidecover actuating. I tracked it down to the ignition wire by popping the fuses in and out and that's the one that actuated the relay. Now when I check my diagram I saw that the sensing circuit/brown wire out of the regulator also is power to the ignition fuse. When I was checking that out I thought I'd short one side of the fuse and see if the engine died like when I ratteled the fuse box, (obviously not a great idea, but theoreticly would show me that a short there would have the anticipated effect) attempt one I burnt the fuse instantly, attempt 2, with a new fuse, on the other side of the ignition fuse holder the short sparked but didn't kill the engine, and I quickly dropped my lead because it started smoking. Funny thing is after that the relay stopped clicking when I ratteled the fusebox and when I rev my engine it only goes up to 14 volts DC like it used too. All I can think is that there really was a short somewhere else and I got the plastic on the wire just melted enough that it insulated again? Any other ideas what the hell just happened?

    P.s. Pics are of my janky fusebox and the relay under the left side cover. Yes I know I need to replace with blade type fuses, I just haven't done it yet. Mostly because I couldn't ride to the store to get the supplies I needed
  8. DanielBlack

    DanielBlack XS650 Junkie

    You're not only looking for shorts, which are connections that shouldn't be there. You'realso looking for non-continuity, the absence of connections that should be there.

    The intermittency of your fuse block is a good example. When the motor was running and died when you shook the fuse block you temporarily disconnected the ignition's power. Look for dull, greenish copper (signs of oxidation) and scorched copper and brittle, cracked, discolored insulation (signs of intermittency caused arcing).

    But really, if you haven't done so, go through every single connector on your bike and be sure each terminal is clean, bright, shiny copper. Then smear a little dielectric grease on them to keep them that way. Last, be sure each connection is snug and solid with no strain pulling on it.
    Last edited: Aug 6, 2017

    DESTROYASAUR XS650 Enthusiast

    So I was wrong. It's definitely still overcharging. But only above about 6k.

    In relation to all the connectors, I've already cleaned as best I could and smeared dialectic grease In all of them. Frankly almost all of them allready had it done when the bike came to me.

    On the subject of continuity, I'm getting vwry jumpy continuity readings going from the brown wire at the regulator connector to the brown wire at the posative brush with the brush disconnected. When the brush is connected I'm getting continuity but I'm guessing that's from the other end?

    Also, just in case it matters. My reserve lighting relay seems to have been removed and the side stand switch diconnected. At the reserve lighting unit the wires have been cut just past the connector and the blue/black stripe and te blue/yellow stripe seem to have been connected.

    I'll dig more into the poor continuity between brown regulator wire and brown wire at the brush but I suspect it may have just been my probing from the back of the connector. If that continuity checks out and I'm getting battery voltage at the brush does that mean my sensing circuit is probably good?
    Bob Kelly III likes this.
  10. mrtwowheel

    mrtwowheel Honda Etched On Brain Top Contributor

    Those crimp on connectors could very well be your problem, and those glass fuses will probably cause a problem down the road. Maybe not your charging problem, but they will be a problem.

    If you have to use those crimp on insulated connectors..........do this, cut the plastic off of those connectors, then crimp them on the wire, solder that crimp with electrical/lead containing solder and cover the crimp with shrink tube.

    Always suspect those insulated crimp on connectors to be a problem, now or waiting to happen.

  11. DanielBlack

    DanielBlack XS650 Junkie

    The brushes having good ground and battery voltage respectively is necessary for good hot voltage production, but that doesn't seem to be your problem.

    Your issue is not being able to turn it down. That's ~14v or more on the sensing circuit.

    You could try placing a fused jumper between the red positive battery lug and the regulator's sensing wire, bypassing the 35yo wire and fuse block. If that doesn't fix the problem I'd suspect the regulator.

    Get rid of the fuse block. It's notorious and an easy upgrade. Yours is a proven problem.

    DESTROYASAUR XS650 Enthusiast

    So, I certainly have that continuity from the brown regulator wire to the posative brush, the signal fuse, the ignition fuse, the headlight fuse, and the key switch. Checking for voltage drops now to see if I can find that short.

    Just to clarify again. I'm only checking the brown wire from the regulator plug to the brushes, the key switch, and the fuses right? Any shorts after the fuses would have blown the fuses so we can assume that whole area is safe?

    DESTROYASAUR XS650 Enthusiast

    Ah wow, didn't see all these replies. I'll look into those things now. Thanks guys! And yeah, that fuse box is going to be going tomorrow. Any recommendations? I was just going to get everything from oreiley, but if you guys have a better suggestion I can also buy from the Internet.
  14. mrtwowheel

    mrtwowheel Honda Etched On Brain Top Contributor

    Dielectric grease is not a conductor. Dielectric grease between two metal parts that are supposed to make an electrical connection is a "dirty" connection causing resistance. Take the flak, but have better connections.

  15. DanielBlack

    DanielBlack XS650 Junkie

    I'm not too familiar with the later reg/rect wiring scheme, but I suspect the wire connecting the regulator to the positive lug. Any wire, connector, fuse, etc. along that chain is suspect.

    Also, I doubt a short. I suspect dirty, loose connections. Brittle, stiff wire.

    Use the jumper test described above or do a continuity and resistance test of the sensing wire.

    Turn your VOM to it's lowest OHM setting. This measures resistance to electricity glow. Touch the two leads together you might get up to .7ohms. Be sure you're not touching the probes with your fingers and the reading steadies. Remember this base number, you'll subtract it from your further readings.

    Now touch one lead to the positive lug and the other to what connects to the regulator's sensing wire. With the base number subtracted, you're looking to see 0 ohms, showing a good clean path.

    Have you checked what voltage you have on the sensing wire at higher revs? If it's lower than battery voltage, wiring is the problem. If it matches battery voltage, it's likely the regulator.
    robinc likes this.

    DESTROYASAUR XS650 Enthusiast

    Okay, I did the continuity check on the sensing wire between the regulator plug to the brushes, to the key switch, and to the fuses. Good continuity on each of those.

    I also did the jumper test and still got over charging at the battery.

    Lastly I checked the voltage at the sensing wire at the regulator plug and at high revs it showed over charging. I didn't have two volt meters handy but it seemed to progress towards overcharging in much the same fashion that my test between the battery terminals showed.

    So, from what I've been hearing that really seems to point to my regulator? Even though my bike passes the slap test with flying colors?
  17. DanielBlack

    DanielBlack XS650 Junkie

    Yup, to me it sounds like the regulator is stuck in the 'on' position.

    Particulars about the regulator itself are beyond my knowledge. Yours is the late style regulator, different from my early 77.
  18. mrtwowheel

    mrtwowheel Honda Etched On Brain Top Contributor

    For about $15 you can get a VR38SB from NAPA, make three wire connections and check the charging voltage. I'm not sure about the mounting of this regulator on your bike, but I'm sure it's been done.


    DESTROYASAUR XS650 Enthusiast

    Great! Thanks for all the help DB!

    Scott, could you elaborate about that vr38sb. Is that a regulator? My bike has a combined regulator/rectifier. Would that be a replacement or just a short term quick thing to check if a new regulator fixes the over charging? if yes then I'd need to buy the actual unit meant for the xs?
  20. mrtwowheel

    mrtwowheel Honda Etched On Brain Top Contributor

    No, this is a permanent fix. By unhooking the regulator part of your reg/rec you can still use the rectifier part of your reg/rec, wire in the VR38SB regulator.

    Don't buy any parts yet. I'm not sure about the wiring or mounting on a combined reg/rec model.

    Let's get someone to verify this.

    Anyways, for only a few bucks you can have a reg to substitute and check your old reg. against.


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