Charging/Low Voltage

Re: Charging/Low Voltage

Postby the_big_h » Fri May 19, 2017 12:58 pm

PFox wrote:A short on an output will still show full voltage on that output. It will show 0V, or in the case of a battery the battery voltage, on the far side of the short.

A regulator/rectifier only has so much current to give.


Going through and verifying that the positive wires in the system are not low resistance to ground is not a distraction, it is a basic troubleshooting step. Especially given the lack of obvious breaks in the wire directly between the two.

Additionally: by the wiring diagrams it looks like the brown wire goes through switches before it hits the lights, horn, etc. So if it's reading 0 without that switch on, that's DEFINITELY a problem. A pinch, a small short, a kink.


Sorry, I didn't mean to say you are getting sidetracked by bad advice, on the contrary, I agree you need to take in the whole picture.
What I mean is that trying to find a problem where a wire that should be "open" reads 93K to ground. The current through 93K from 12V is about 0.1 mA, would drain your battery in about a year. Insignificant.

I agree the R/R has only so much current to give, if you draw more current than it can give, it's output voltage will drop. This first post in this thread said 14V at the R/R (so it's not overloaded), but 12.7 at the battery at the same time. Therefore the regulator does not have a solid connection to the battery. Period.
A further post indicated 200mV drop between the R/R and the battery - but this is inconsistent with 14V compared to 12.7V. Either one set of readings is incorrect, or the other - 14 minus 12.7 = 1.3 volts, not 200mV. If it's not in the positive, it's in the ground.
The wiring diagrams are difficult, and they don't show what's in the connection box, so it's hard to determine what is what (it's possible there are errors in the wiring diagram also - the fan circuit doesn't look like it could work, and are there really 2 different uses for Yellow/Black?. I've proved errors in factory wiring diagrams before....)
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Re: Charging/Low Voltage

Postby Rakillia » Fri May 19, 2017 4:08 pm

Electrical is my weakest subject when it comes to working on bikes. Which is why I'm not terribly upset about this because its giving me the opportunity to learn something. Everything on that Red/Blue wire is lights. The only way to get it to not beep to ground is if I disconnect all the lights. There are definite issues with the wiring. The fuel gauge always says a full tank which I now know means its shorted. My voltage numbers aren't really gospel. With the meter jumping around and the rpm's jumping around its more of a ball park reading. But it is true that I'm losing about a volt between the R/R and the battery. If all I need to do is replace the positive wire I probably have that laying around the garage. I could even bypass the junction box and where it connects to the starter solenoid and attach it straight to the battery. The harness looks factory. Someone has been in there but all the connections are intact and look original. I took the junction box apart. It doesn't look great in there but all the connections are reading zero ohms. The only pin not reading right is part of the kickstand switch. Which I would just as soon bypass anyways. I could post pics of it if anyone is interested. Also I put the full manual in my dropbox.

https://www.dropbox.com/s/h67s8b6g9gh5s ... y.pdf?dl=0
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Re: Charging/Low Voltage

Postby the_big_h » Fri May 19, 2017 7:09 pm

Yes, any lights will beep to ground, this is normal, the resistance of the light bulb is low enough to make the meter beep "continuity". This is normal, is not a problem. If the bulb circuit really was shorted to ground, then a fuse (assuming there is one in that circuit) would blow. If there was no fuse, the wiring would get hot and melt. Reading open circuit with all the bulbs removed is good also, this is expected.

Losing about a volt between the regulator and the battery is a problem. In my opinion this is where you need to focus your efforts. Running a temporary wire direct from the R/R to the battery could confirm if there is a problem in that part of the circuit. I've had trouble before with the connections at the solenoid, on my Sabre the connector melted from a bad connection there.

The kickstand switch would not normally be part of the charging circuit, I can't believe it is related to your issue of not charging.
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Re: Charging/Low Voltage

Postby Rakillia » Fri May 19, 2017 8:09 pm

Yes the charging is the main issue. I don't care if the fuel gauge works but it does say that something else is going on. On the vulcan forum the junction box is a source of many electrical problems and a lot of people have either modified or done away with it completely. The white wire coming from the R/R does go through the 30 amp main fuse. If I went straight to the battery I'd have to put an inline fuse on it. But for testing purposes it should be fine.
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Re: Charging/Low Voltage

Postby Rakillia » Tue May 23, 2017 12:58 pm

Getting better. Now I'm losing maybe 1/2 a volt. I swapped the R/R. I just didn't have a good feeling about it. Now the resistance between positive and negative is gone. I took a 12 gauge wire, stock was 14, and went from the jb straight to the battery. I could have gone from the R/R but it would of been a lot more work and require an inline fuse. I need to put everything back together and put the tank back on so I can check again but I think its ready for a test ride. Still have the weird issues in the dash but as long as it isn't effecting the important stuff I'm done with this.
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Re: Charging/Low Voltage

Postby Rakillia » Tue May 23, 2017 3:57 pm

Found the 1/2 a volt. From the R/R ground to the battery ground.
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Re: Charging/Low Voltage

Postby Rakillia » Tue May 23, 2017 4:59 pm

vulcgr.jpg


Didn't think it would be this difficult but, The wire from the R/R goes to the splice by my thumb, then to the splice by my pinky, then to the bullet connection on the right of the pic, then to the battery ground. I thought the whole point of using the frame as a ground was so you didn't have to run so many wires. Can I just cut the wire by the 1st splice and run a new wire from the R/R directly to the battery terminal?
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Re: Charging/Low Voltage

Postby the_big_h » Tue May 23, 2017 8:11 pm

Yes, you should be able to run the R/R ground directly to ground, without having to go through a bunch of connections.
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Re: Charging/Low Voltage

Postby Rakillia » Fri Jun 02, 2017 8:42 pm

Fixed. Ran a new ground wire from the R/R. Put a ring terminal on and bolted it to the same place the negative battery lead is bolted to the frame. Now the voltage is within a few tenths. It's still down on power but it shouldn't leave him stranded. I had to get this out of my garage so I can rebuild the transmission for my truck.

Thank you all very much for the help. I was really lost. Now I know ohms don't mean anything and to measure the voltage drop.
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