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  1. #1
    CB750 Member nightengale's Avatar
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    turn signals not working

    Hi - first post. Picked up a very low mileage '82 CB750. Have a few issues I could use some advice on as I try to get this road worthy.

    Turn signals light up (running lights on front), but don't flash (they turn off when turn signal is activated). There is a fat round solenoid mounted next to the battery and a loose solid green wire that I can't figure out where it goes.

    Is this the turn signal solenoid like I think it is? What is the solid green disconnected wire supposed to go to? It's got a factory spade connector that goes somewhere, but there isn't anything within reach of the wire length.

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    Thank you in advance for any tips on this.
    Last edited by nightengale; 07-21-2019 at 01:25 PM.

  2. #2
    CB750 New Member Intense951's Avatar
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    Thatís your turn signal relay. On my 1980 750c, the green wire just hangs out. It isnít supposed to hook up to anything. I replaced the relay on got my rear blinkers to work. From reading other forums yours sounds like it might be a grounding issue. Look up the wiring diagram and go through your grounds and/or replace the relay.

  3. #3
    CB750 Guru amc49's Avatar
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    I'd swear I answered this post as well and even saw my answer after it posted..........???????

    Anyway, that is correct. Honda had the possibility of two types of flasher there and one grounded, the other didn't. The wire simply hangs loose in space when not needed.

  4. #4
    CB750 Member nightengale's Avatar
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    Quote Originally Posted by amc49 View Post
    I'd swear I answered this post as well and even saw my answer after it posted..........???????

    Anyway, that is correct. Honda had the possibility of two types of flasher there and one grounded, the other didn't. The wire simply hangs loose in space when not needed.
    I found a new automotive two-pole relay - installed it and it did not work (fix the problem). Honda wanted nearly $30 for the part (if they could get it ordered in), so I thought I'd try the cheaper version at $7.95...

    I have not tried chasing down the ground wire issue mentioned yet... but I know that the battery is properly grounded, but haven't checked for other ground wires yet, but will next.

    I do have a horn "problem" too (doesn't work), so perhaps they are related.

    The bike was complete (all stock, nothing missing) except for the positive battery lead, so I built one of those. Also needed a new battery, got that too.

    Good to know that the loose green wire doesn't do anything, thanks.

    Am I assuming correctly that the turn signals WILL flash if the bike is NOT running (ignition is on)?

  5. #5
    CB750 Member nightengale's Avatar
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    Well, that was stupid... was moving that loose green wire and it touched the positive on the battery. Sparked for a second, now I've got nothing (no lights/ignition). So I probably blew a fuse. Main 30 amp fuse still looks ok, and so do the glass fuses on the dash. Where is the so-called "inline fuse" located that I've read about? Obviously, I killed something in my ineptitude.

  6. #6
    CB750 Guru amc49's Avatar
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    'Am I assuming correctly that the turn signals WILL flash if the bike is NOT running (ignition is on)?'

    Yes. The battery must be fully hot.

    The car flasher WILL work if the system is right, I use nothing but them and for years. The number 552 sticks in my head but that may be the 3 prong one, would work using the extra ground. The 2 prong is more trouble free.

    The horns tend to get water or humidity inside to go bad and then you must damage them to get them open to clean it up and back to working fine, but next you have to find a way to clamp the outer case back together.to still look nice. There is a small screw on horn outer that if you mess with adjusts the steel diaphragm, sometimes that can make it begin to work too.

    The main 30 amp IS the inline fuse. Looks like thick aluminum foil strip. They can suddenly corrode to turn into dust, I commonly replace them with a good weatherproof inline fuse that cars use to make it easy to replace one.

  7. #7
    CB750 Member nightengale's Avatar
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    Quote Originally Posted by amc49 View Post
    The main 30 amp IS the inline fuse. Looks like thick aluminum foil strip. They can suddenly corrode to turn into dust, I commonly replace them with a good weatherproof inline fuse that cars use to make it easy to replace one.
    I tested continuity on both sides of the main fuse and it's fine. So I think I fried something else altogether, but at the moment, am at a loss as to what it might be.

    Is there anything I can check at the ignition switch? Any inline fuses in there or perhaps a relay? I haven't pulled it out yet.

  8. #8
    CB750 Guru amc49's Avatar
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    No relays used on bike other than starter and flasher. The main fuse and then the handlebar block of fuses. Of course somebody could have added a main somewhere else. Ignition switch could have fried contacts inside it.

    Test fuses for power at both sides, I've seen them blow weirdly inside at one end to where they look fine but aren't. Crap solder point at the end of the fuse wire.

  9. #9
    CB750 Guru amc49's Avatar
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    Went looking at the SC schematic (you said '83 model) and that particular short would have gone directly into the regulator/rectifier to come out literally anywhere for a good bit before hitting any fuses to blow out. Not good news, could have damage in a lot of places.

  10. #10
    CB750 Member nightengale's Avatar
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    Correction on the year - 1982.

    I followed the Clymer instructions to check the regulator/rectifier, need a little clarification.

    Testing the leads, connect the ohm meter to the green wire and then testing each of the 3 yellow wire (page 201 in my manual), I get 4.03 ohms across all leads.

    Then, they want you to reverse the tester leads and repeat this step. I get just 1 across all the yellow wires (no change at all - see comment below). I'm "supposed" to get "opposite measurements" from the first test, according to the manual. If you got low in the first test, then this test should read high. This seems to me to indicates I know have a bad rectifier, although it's VERY unclear what they consider "high" and what they consider "low".

    If I'm getting 4.03 and then switching leads, and getting 1 (or less, see comment below) is that a "opposite" reading? Yeah, I very much dislike Clymer manuals...

    My Greenlee tester reads 1 ohm basically at all times by the way, I assume that's normal.

    Yeah, kicking myself for that stupid short fumble. That sort of thing never happened to me before.
    Last edited by nightengale; 07-21-2019 at 01:34 PM.

  11. #11
    CB750 Guru amc49's Avatar
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    You are checking diodes there, the rectifier portion. Diodes can only be tested by a specialized diode function on the VOM meter and not all have it. Most VOMs do not pass enough current through the diode to activate the one way pass through function, there needs to be a certain amount of amp there to trigger that function and what the diode test does if the meter has it.

    While one ohm is very low, there are lots of things that require precise answers under that to be reliable, I would not use a tester that cannot go lower on a routine basis. Tester needs to be able to get into .1 territory all day long.

    Normal result on a good diode will be like close to zero one way and infinite the other, or in the thousands or millions.

    All you can check there is rectifier, the only good check of the regulator portion is part mounted on bike and engine running, there are simply way too many ways that part can fail to not be tested accurately.

  12. #12
    CB750 Member nightengale's Avatar
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    Ok, that makes sense. I found this vid: https://www.youtube.com/watch?v=ted0_4On29M and the rectifier "passed" these tests, including the powered black lead with the key on. So now I'm thinking the zero power situation is something else (got fried), not the rectifier.

    I can ask around, but don't have access to a better tester just yet. I live in the sticks too - so getting tools, parts, food, etc., it's a job in itself.

    Did check the main fuse (again), it's fine. Tested continuity on all handlebar fuses, they're fine.

    What is that small removable black block wired into the main harness, behind the main fuse? Pic below. No continuity on this device. What does it do?

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  13. #13
    CB750 Guru amc49's Avatar
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    Another bigger load carrying diode. It simply stops current backflow from going backwards in system due to the clutch switch arguing with the engine neutral switch as to which has power priority when the safety interlock works to stop engine cranking up in gear. It tests the same way the rectifier diodes do, one way power flows and the other way not.
    Last edited by amc49; 07-21-2019 at 10:49 PM.

  14. #14
    CB750 Guru amc49's Avatar
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    After some thinking I would suggest you go over the main grounds at battery and chassis ground. The short directly into that ground wire would have taken the path of least resistance to continue in the ground to get to battery on other side. It may have melted right at bolt on ground points. If not then worse, the power went backwards into every piece of solid state you got there like the ignitors as well as the VR.

  15. #15
    CB750 Member nightengale's Avatar
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    Quote Originally Posted by amc49 View Post
    After some thinking I would suggest you go over the main grounds at battery and chassis ground. The short directly into that ground wire would have taken the path of least resistance to continue in the ground to get to battery on other side. It may have melted right at bolt on ground points. If not then worse, the power went backwards into every piece of solid state you got there like the ignitors as well as the VR.
    That "Stanley" diode checks out fine - I didn't check both "directions" the first time as I should have.

    The "shorted green wire" only barely contacted the positive very briefly, probably not enough to my thinking to fry any 18 or heavier gauge wires, but it still certainly killed the power somewhere. More likely (again to my thinking of course), it fried either a fuse or a diode somewhere that is preventing any of the power to come on (no dash lights now, no starter). But I admit to just guessing here, I know how fast electricity travels.

    The battery ground is solid, clean, etc. Found another ground by the coils, same condition, it's good. Can you point to any other ground points?

    "VR" means Voltage Regulator? If I had a spare one of these, I'd just swap one in to check things for function. I can ask around and see if I can track one down somewhere "nearby".

    By the way - thank you for your advice, it is most appreciated. I did check the Greenlee manual for ohm's sensitivity, you're right on this too, it's definitely not sensitive enough. Only goes down to 1.

  16. #16
    CB750 Guru amc49's Avatar
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    The problem if you follow the circuits is that the short had to go through any electrical component BEFORE it gets to a fuse, follow the direction there. You put power into the ground and then it ran up every ground in a backwards direction, the classic reverse polarity short. Most of the force should have simply followed the main ground back to battery.

    There is only one main harness/frame ground, all grounds in the harness tie into that. The oil pressure switch, neutral switch, front turns, starter case, have dedicated grounds and there is a ground inside headlight shell too thinking.

  17. #17
    CB750 Member nightengale's Avatar
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    Installed a used voltage regulator (purchased from a cycle supply - I'm assuming it's good). Still have no power, no dash lights, etc., however, in Park mode on the ignition, I get a rear tail light to turn on. Can't recall if I checked Park mode before, don't think so. So that regulator swap didn't seem to work... Did test the black "key on" lead, it works.

    What about the main fuse starter capacitor? Is there any way this component can be tested for function? The main fuse is fine, but it's got that big capacitor that is "next in line" on the reverse polarity direction. I don't know if the capacitor would impact the dash lights staying off or not.

    Basically the same question applies to the ignitors - if they've gone bad - does that affect dash lights and power outages like this?

  18. #18
    CB750 Guru amc49's Avatar
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    Black ignition lead having power with key on says all fuses should have power to them, do they? If so the neutral and oil lights should be on at key on, are they?

    There is no starter capacitor and not needed, that is a relay and only works with starter button pushed down.

    If ignitor power shorted before or at them of course the power short could stop all power to bike, take note of anything getting very hot with key on, an indicator of where it might be.

    Park position is taillight on only, to keep from being run over say stopped on side of road broke down.

  19. #19
    CB750 Member nightengale's Avatar
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    With key on, oil pressure and "head" (whatever that is supposed to mean) have no power. Turn signals, tail and horn do have power. Nothing gets warm to the touch (regulator, ignitors, fuses, starter relay) with the key on.

    Is there a way to test ignitors?
    Last edited by nightengale; 07-23-2019 at 04:59 PM.

  20. #20
    CB750 Guru amc49's Avatar
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    'Lead' not 'head', the black ignition power wire you said before had power. You used the word yourself..........

    'Did test the black "key on" lead, it works.'

    That 'lead' supplies the fuseblock at all positions with the same wire and having turns, brake and horn but not others says fuseblock has something wrong with it. You need to test for power at all fuses with key on. You should likely get it on BOTH sides of each fuse.

    Ignitors do not really test other than by switching to a known good one similar to the VR. Too complicated, simple voltmeter testing does not indicate all the things that can be wrong there.

    Gonna toss you a curve ball that often shows up with severe shorts. If you take a wire that works fine with say 35 strands of copper in it and then melt it almost in two, to where say only 2 strands are all that are carrying power, the others have melted in half, then you will get voltage showing there on a voltmeter but the things getting power will not work due to not enough wire left to carry the correct amount of power to work the device. So, beware.

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