charging

[GLoweVA]

I did TC's fuse box almost 2 years ago and love it.
I've had a few oil leaks in the past year, so everything under my tank is pretty much covered in oil and dirt. I'm sure most of those connectors are all cr*pped up. (especially my turn signal plug. I think that's where my issue is)

[Elwood2]

today I tested the regulator and again I find a plug the has a wire that stops at the plug. This time it is the black wire. last time it was the yellow wire with the white wires on the stator. Are these suppossed ti be like this? Anyway my readings were .01 black/green manual says less then 1.8. So its in spec bet that sure seems low to me.wil bike was running 10.48 manual says betwwen 9 and 11. black /brown I got 10.54 manual says 14.2 to 14.8. So way low there. Then the manual says if step 3 and 4 are not met replace regulator, but the low volts I got with the black and brown wire were step 5 and it does not say what to change when that is out of spec. Also while testing my tach was not working and head light would brighten with revs. tach didn't work after I tank back on but then started working after I walked away for about 10 mins. headlight still brightened with revs. Again thanks for the help...

[Geezer]

The missing black wire is a redundant ground that Yamaha decided to save a nickle per unit and eliminate.

Geezer

[GLoweVA]

That black/green reading it TOO low!.
You did do the checks with the connectors connected right?
If they weren't connected, then those readings make sense.

Previously you posted that the ohms are good on the stator and field, so those are good.
But in order to produce voltage, the alternator needs voltage supplied to the field. On both my bike and Nightengale's we saw about .9Vdc on the field. (Black/Green)
If you're not getting anything there, then your regulator/rectifier is bad.
I just picked up a replacement on ebay for about $15.
Look for 750/850/1100 77-81 all those years will be the same.
Also Andreas in WA has one and he's a whole lot closer to you than he was to me.

Curious that you say the headlight gets brighter. That's an indication that the system is charging and you should have seen that at the battery voltage going up while reving.
As far as the tach goes, that gets its signal from one of the 3 white wires that come from the stator. One reason it could have cut out and then came back is a loose connection for the gauge/tach.
Then again, if the stator output is low or intermitent then your tach would follow that and the charging would also be erratic. (off/on)
Maybe you've still got a loose connection somewhere.

Another thing to note is the headlight relay also gets power from one of the stator wires via a diode. That way the headlight doesn't come on until the alternator puts out some output.

I hope all this helps. I'm keeping an eye on this thread and will offer up anything else I can think of.

[Elwood2]

My headlight comes on as soon as I turn the key on. So somwone
may have rewired it.

[GLoweVA]

My headlight comes on as soon as I turn the key on. So somwone
may have rewired it.

Mine does too, but I've jumpered out my headlight relay.
The headlight relay sits just under the tank all the way near the front of the frame. If your's has been modified, it's probably been done there.

[Elwood2]

So I pluged in the regulator plug this time while testing lol. First I checked the battery with everything off, 12.4volts. Started the bike, it read less then 11 and didn't read above 12 until about 4000rpm. next I redid the regulator volt check. I got .92 on the black/green with key on and not started. I started it and it dropped to .83volts. Then on the black/brown wire I got a reading of 10.32 at idle and it went up to 11.03 at about 4000rpm. So is me regulator bad? Money ie REALLY tight, I'm currently a full time student so I don't have the funds to just start replacing things that don't need it. Thanks for the help everyone.

[GLoweVA]

So I pluged in the regulator plug this time while testing lol. First I checked the battery with everything off, 12.4volts. Started the bike, it read less then 11 and didn't read above 12 until about 4000rpm. next I redid the regulator volt check. I got .92 on the black/green with key on and not started. I started it and it dropped to .83volts. Then on the black/brown wire I got a reading of 10.32 at idle and it went up to 11.03 at about 4000rpm. So is me regulator bad? Money ie REALLY tight, I'm currently a full time student so I don't have the funds to just start replacing things that don't need it. Thanks for the help everyone.

Elwood, Those numbers seem okay, but low, to me. I seem to recall almost the same numbers on my bike and John's and our bikes weem to work okay.
I suppose you could do the ohm check on the regulator diodes. I did this check on John's and it showed that he had some bad circuits in there. But he also only got about 6 volts on the output then.

Maybe you've got a bad connector somewhere that's limiting the voltage to the battery and thus limiting the amount of charge it gets.

Something else you can try that's not in the book, while the bike is running, put your meter on AC volts and check the white to white to white voltages. You should see something like 12-16 Volts AC. Maybe one of these is bad/low and thus dragging the whole circuit down. One of these white wires is supposed to feed the tach and the headlight relay. If one of these is bad and drawing too much load, then that would drop the total that the rectifier puts out.
You could disconnect the headlight relay and the plug that feed the tach. (unfortunately the tach plug is in the headlight bucket)

Another thing to try is to pull the fuses for everything but the ignition fuse. (headlight, taillights, brake lights) This will shed some load off the bike and may free up the rectifier/regulator to show you that it's working.

That's all I can think of right now.
If your regulator is toast, I may feel generous and send you the one I just got in the mail for my project. (one of those 'pay it forward' things)

[bikerphil]

Another trick to see if your regulator is toast is to tap into the dark green field coil wire coming from the alternator and connect to ground. This will bypass the regulator and give you full charging voltage. This test is safe temporarily for diagnostic purposes. Now check the voltage at the battery with the bike running and see if it improves.

[GLoweVA]

Yellow wire

Elwood, I've been looking at the wiring diagrams for the 80SG (which should be the same for the LG)

Also on the plug with the white wires is one yellow wire what is it and where does it go? on my bike the wire stopps at the plug.

You say that one of your plugs has a yellow wire in it.
The SF wiring diagram has a yellow wire coming out of the connector and going to the 79 headlight relay. The question is which direction is your yellow wire going? to the stator, or to the wiring harness?

Okay, so while typing this up I went out and looked at my SG, sure enough, there's a yellow wire coming from the stator that stops at the connector behind the fuse block. Looks like I answered the question.

Phil, That will supply a full 12 volts to the field coil and thus you'd get alot of output from the stator and the rectifier/regulator should limit that to the 14.2 to 14.8 Vdc.
I like this test, but if it works, what does it really tell you? Where do you go next?

[Elwood2]

I suppose you could do the ohm check on the regulator diodes. I did this check on John's and it showed that he had some bad circuits in there. But he also only got about 6 volts on the output then.

do I test it not running unplugged, plugged in or running unplugged, plugged in?

[bikerphil]

Phil, That will supply a full 12 volts to the field coil and thus you'd get alot of output from the stator and the rectifier/regulator should limit that to the 14.2 to 14.8 Vdc.
I like this test, but if it works, what does it really tell you? Where do you go next?

I've seen over +15VDC doing this test at 5K RPM's, the regulator will not limit the voltage at all with that wire grounded, I can't tell you (don't know) the specifics of why. It pretty much just determines if your alternator is bad or if your regulator is weak/bad.

[Elwood2]

good to know that the yellow wire is supposed to stop at the plug, wonder why it's there in the 1st place

[Elwood2]

while testing the regulator the black and green tested at .92 with key on, bike not started. when the bike was running it dropped to .82. in the manual it says it should go up to 9 to 11 volts. That seems way off to me but I don't know if it is the regulator or not. Is that the same green wire you are talking about grounding? isn't that what I did with that test? Thanks for all the help

[GLoweVA]

Unplugged

Undo all the connectors to the regulator.
The manaul says to check white to red and white to black.
Check with meter on ohms (at least 550ohms)
Black meter lead on the red connector and red meter lead on the white connectors. (all 3 should be about 500ohms)
Red meter lead on the black connector and black meter lead on the white connectors. (again all 3 should be about 500 ohms)
DO the reverse and you should see an open for all six of the checks.

I just checked this with the one I got in the mail. all good.