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'79 special voltage regulator swap basic questions

Discussion in 'The Garage' started by pkovo, Apr 12, 2015.

  1. pkovo

    pkovo XS650 Enthusiast

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    Thanks Guys. I'll have to read all this a few times, especially your post twomany. Kind of flew over my head.

    The relay idea is a good one. I've searched through a lot of threads on this, and I don't recall seeing anything on that. It's interesting, and seems like it would be cheap and easy really.

    Following Leos reply, I have zero drop on the red wire through the fuse up to the switch, and now after cleaning the switch it has only about .015v drop, which I thought was pretty solid for a 37 year old switch. I cleaned up the contacts well, but they are grooved. Even though it's not on this path, I also took apart and cleaned the kill switch as it had a drop, and that one is almost perfect now, reads a drop of .001. Thing is, I didn't really trace and clean connections on the brown wire back to the reg plug. Looking at my diagram, it kind of seemed like a straight run, but I know it has the rest of my .2v drop, so a cumulative drop of .185v. I thought that was actually pretty acceptable, so I stopped. I guess though, if I clean most of that up, I should theoretically be right at 14.5v charging, so it's probably worth it.

    My battery is an AGM type, and its the first of this type I've had. I would hate to kill it prematurely, but by the same token, I don't think my slightly high voltage readings will destroy it in quick order, especially how I plan to use this bike. Mostly a backroad sunday rider, shorter hops, no sustained high speeds.

    All my tests running are with loghts on, as I have no switch to turn them off. I tested with the low beam on only. I meant to see how the high beam would effect the voltage, but keep forgetting. If the high beam drops it .2v, hell I'll point the lioght down a little more and run with the high on. I don't ride at night anyway. I also have a sealed beam auto headlight up front, but that's been on there for a long time. I probably should look at what it draws.

    Voltmeter is on my short list of needs, just haven't found one I liked yet. Brushes and a few other doodads from MikesXS are on my extra short list.

    Thanks again.
     
    Last edited: Apr 20, 2015
  2. pkovo

    pkovo XS650 Enthusiast

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    Just measured voltage with the high beam on. To my surprise, voltage went up.

    Also measured across brushes with bike running Starts at 10.Something volts at idle, but as the revs increase, the voltage climbs and as it goes past 12v, my meter spazzes and can't read it. Will try that with a different meter also.
     
  3. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    That's the effect of the regulator regulating the load (brown wire) instead of the battery voltage. The increased current required by the hi beam causes an additional voltage drop across the ignition switch, fuse and other connections. The regulator "sees" this and increases the current through the rotor winding which increases the voltage going to the battery (red wire) but the brown wire voltage remains the same because that is where the regulator is connected and that is the voltage that is regulates, not the battery voltage.

    The mechanical relay type of regulator is less predictable, but a good quality solid state regulator properly installed will maintain the brown wire voltage at 14.5 but the source of the current is on the other side of the ignition switch, so as the load increases on the brown wire side, the red wire side (battery) has to increase to maintain the brown wire voltage. That's why it is better to connect the voltage regulator to the battery through a set of relay contacts so the regulator will maintain a constant 14.5 on the battery. As the load increases on the brown wire, the brown wire voltage will decrease, but that does not cause any harm whereas an increase in the battery voltage can harm the battery.
     
  4. pkovo

    pkovo XS650 Enthusiast

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    With this, I think I get it, and it makes using a relay a more attractive option. SInce you mentioned you put the relay on your bikes, in your experience, any specific relay preferred, or just any automotive relay with the right specs ok? If I go this route I'll mount it creatively to attempt and insulate it from the vibes of this thing to some degree.

    I just pulled the plug on the headlight all together, and without that load, my charge rate is 14.4-14.45 at 2-3k.

    I'll still probably try and clean ALL my connections up to decrease the overall voltage drop, but as you mentioned in your first post, with the relay approach, a slightly dirty connection won't be such an immediate concern.

    I also checked voltage at the brushes with another meter. This meter didnt spazz out, it showed what I expected to see, voltage drops at the brushes with higher revs.

    Thanks Again.
     
  5. Its normal to see 10 to 13 volts across the brushes with the engine at 1200 rpm.
    Rev the engine up to 3000 rpm or more and the voltage across the brushes should decrease to 5.5 to 7 volts. That change in brush voltage, shows that the voltage regulator is working correctly.
     
  6. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    pkova,

    I used this relay which is commonly available at most auto supply stores for about $5:

    [​IMG]

    However, as I mentioned, you won't necessarily get predictable results with the original stock relay type of regulator. You need a solid state regulator.
     
  7. pkovo

    pkovo XS650 Enthusiast

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    Thanks. I pulled the stock regulator in favor of a VR115 equivalent right after starting this thread, so I should be good in that regard. The relay makes too much sense to ignore. I'm wiring one in.

    I'll still sweep through and clean up the rest of the wiring though. Every connection and the two switches I've cleaned thus far has made a difference, albeit each one small, but the cumulative effect adds up. Plus, not a bad idea just to get eyes on all the wiring, it is 36 years old after all. I replaced the battery cables at the start, and they were just awful.

    Now, if my new rectifier would only get here. They must be shipping it from China by canoe.
     
  8. pkovo

    pkovo XS650 Enthusiast

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    Thats exactly the drop I was expecting to see revved up, but with my first meter, it just went berserk. When I retested with my second meter, in was between 6 and 6.5V, so it must be something wacky with that 1st meter. Or the person using it...DOH

    Ironically, I was doing that based on a post of yours I found in another thread, with these numbers.

    You guys have a ton of information on these bikes crammed into all these old threads. Definitely a hell of a nice support system for the electrically challenged like myself.

    Thanks!
     
  9. pkovo

    pkovo XS650 Enthusiast

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    Put the relay in so now the regulator is using a dedicated line from he battery for its reference point. It now holds a rock solid 14.3v at 2-3k. Also cleaned and replaced a lot of connections for good measure.

    Thanks again to everyone for the help.
     
  10. pamcopete

    pamcopete Ride.Enjoy.Life is Simple


    That's excellent. :thumbsup: You should also experience some of the side benefits as well, such as longer battery life and longer rotor life because with the stock arrangement, the alternator had to produce an extra 1/2 to 1 volt which cooked the battery and meant higher current to the rotor. :eek: Replacing the rectifier will yield additional results because the stock rectifier dropped more voltage necessitating the alternator to produce more as well with the resultant higher current to the rotor.

    Note: You should include an inline fuse for the regulator from the battery to the relay contact. Use a modern low loss fuse holder.
     
  11. pkovo

    pkovo XS650 Enthusiast

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    Thanks Pete. I did add a 20a fuse on that line. Used the same style of modern auto inline fuse holder I used to replace the original fuse block when it failed. The kind with the nice waterproof rubber cap. Really like them.

    Kept the fuse under the seat but was able to mount the relay and all the wiring neatly under the side cover. Used all spade connectors and left the original wiring on the regulator in tact. The setup would allow me to bypass the relay just by unplugging and moving wires, in case it fails, and it will also allow me to swap out a regulator easily with no rewiring; Just plug and play so to speak.

    My rectifier came in yesterday so that's next. Have a replacement terminal block for that also, so will rewire all the connections for the rectifier. In my initial check I found one of the connections had backed out of the terminal block slightly and it caused some corrosion in there. I'm just going to rewire all of it.

    Perhaps I'll get to it tonight, but it's Sunday and the weather is nice here, so I'm going riding! Not riding the XS yet, but Going riding nonetheless.

    Thanks again for the help. I'm going o switch it over to a standard pamco eventually, and will likely have questions for you when I do. For now my points are fresh and I want to get all the other kinks squared away and have it running solid before I make that swap.
     
  12. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    pkovo,

    10 Amp fuse might be more appropriate if all you have on that circuit is the regulator.
     
  13. pkovo

    pkovo XS650 Enthusiast

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    Thanks. It is just the reg on that circuit. I'll swap it for a 10.
     
  14. AussiXS

    AussiXS XS650 Enthusiast

    Hi guys,

    Sorry for the highjack, but this seems like the best place to pose the question.

    I have a stock 1978 XS650 Special in burgundy, its all stock wiring with nothing changed. I have screwed the bolt too tight on the rectifier and broken it, so I need to replace it. I love the idea of a cheap DIY option, but I dont have a pamco, its just stock points and normal alternator, also, the regulator is fine and would like to keep it. How would I make the rectifier like the everyone is talking about?

    The guys in JayCar (Australia's version of Radio shack) said that I would need to connect 3 of these in a row to make a three phase. I have no idea about phases or even what the rectifier does. How would I create one of them that would work?

    https://www.jaycar.com.au/400v-35a-bridge-rectifier/p/ZR1324

    From my rectifier I have 3 white wires, 1 Red and 1 black for the ground.

    Thanks for any help :)
     
  15. AussiXS

    AussiXS XS650 Enthusiast

    Arrh, so is there anyway to make that guy in Aus? Geoff is fresh out of those guys, I am seeing him Saturday so I will double check. Is there a cheaper option?
     
  16. When I did the search there were 6 in stock!
     
  17. 650Skull

    650Skull ex spurt not expert

    Michaelo likes this.
  18. AussiXS

    AussiXS XS650 Enthusiast

    Last edited: Jan 5, 2017
  19. You can use that bridge rectifier that you have listed, but you would need to buy 2 of them, not 3 as JayCar said. Each one of the bridge rectifiers has 4 diodes, but to rectify 3 phases that come from your stock alternator, you need to use 6 diodes. So, you could buy 2 bridge rectifiers, and wire it using 4 diodes on one and 2 diodes on the other. There would be 2 spare diodes left over and they are not used. The 2 bridge rectifiers would be mounted on a common heat sink, and then mounted under the battery box, in the same location as the original rectifier. That would cost only $11.00, and bolt them to a piece of aluminum as a heat sink. That is exactly the same as how I did that on my bike.

    Another way is to buy a single 3 phase rectifier from Ebay. Some of those come mounted to a heat sink.
    Here is a link with lots of details:
    http://www.xs650.com/threads/regulator-rectifier.21485/

    Edit;
    The 3 phase rectifier you have listed in post #39 will work just fine for you. You will need to mount it to a heat sink to keep it cool.
     
    Last edited: Jan 5, 2017

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