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Headlight and Dash Light Issue

  • Thread starter Thread starter driverofLYN274
  • Start date Start date
D

driverofLYN274

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Hey guys, I know I'm probably just not seeing it, but I have just started having an issue yesterday where the dashboard lights dim to almost nothing when I turn the headlight on, but only when the bike is running. I went to ride yesterday and noticed that the headlight fuse popped during my pre-ride check so I replaced the fuse thinking that perhaps vibrations had gotten the best of it. I have already upgraded to the Honda R/R as per BassCliff's tutorial and have been checking for loose or dirty connections, but I'm looking for guidance on where to begin. I am getting 12.38 V at the battery removed, at idle, and 4,000 RPM. It seems strange to me that the stator (which is the original, BTW) would just let go all nimbly-pimbly, but I know very little about these charging systems. My thoughts point me toward a faulty R/R, but again, I am no electrician.

To be sure, the bike is a 1981 GS 750L and it still has the stock fuse block and stator, and has a Honda 5-wire R/R. Ran fine and charged great until yesterday when I was playing around with the air box in the morning an shuffling things around. This community has been very helpful and I want to thank you all in advance for your help.
 
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Did you get rid of stator loop to headlight switch? You need to run the charging tests to pinpoint the problem- this 5 wire honda R/R, is it a FH series? Since you were playing around airbox, maybe you disconnected wiring from the charging circuit.
 
Hi,

That is not good charging voltage. Connect the ground wire from the r/r unit directly to the negative terminal of the battery. Clean the fusebox. Clean all charging system connections and the solenoid connections. Test the stator.

Thank you for your indulgence,

BassCliff
 
driverofLYN274 said:
....
I am getting 12.38 V at the battery removed, at idle, and 4,000 RPM. ......
Click to expand...

You are asking why instrumentr lights dim when you turn on headlight.

People are telling to check your charging system, or are telling some ways to improve your charging system.

Let me say that if you have same battery voltage with bike off and with it running at 4000 rpm : Your charging system is not charging. And you soon will not be able to start the engine and may be stranded somewhere.

Now, why does instruments dim when you turn on headlight? Beacuse your charging system is not charging the battery, and battery voltage drops when you add more load. Maybe you can verify that by measurring battery voltage with headlight off and then with headlight on.

.
 
Alright, here's what today yielded: the stator is consistent at 1.7 ohms on all 3 legs and all 3 have infinite resistance grounded against the frame. While checking the harness I noticed that there is a brown wire in the headlight bucket that is disconnected. Is this the sense wire or something? It is not connected to anything and I cannot see anything to plug it into. Thoughts?

Tom203: I'm not sure what you're referring to. My mystery wire perhaps?
 
I have a "loose" brown wire in my bucket also. On mine, it wasn't to be connected to anything as harnesses and other things were made to fit different models (on mine, I believe the wire was to drive running lights on the front signals).

Redman is correct from my experience also:o. Follow this guide http://members.dslextreme.com/users/storagecliff/images/electrical_odd-n-ends.html#A04 to finish checking the system.

You can't be too methodical when chasing/testing the charging system. Start by making sure the connectors are clean and charge the battery (make sure it's good as well). Clean the connectors even if they look clean. At a minimum, there MAY be a problem - it can be as much as just not working right. Dirty connections = resistance = heat. See http://www.thegsresources.com/_forum/showthread.php?t=193842 to what a failure might do.

As a fuse popped, I'd check all the wires/connectors on that circuit. Here's a wiring diagram for your bike (I believe) http://members.dslextreme.com/users/storagecliff/images/750tz_wiring.jpg

Check everything on this list fully complete the items. You're working in #7 on the list. Follow those directions and here is another great reference http://www.thegsresources.com/_forum/showthread.php?t=152769.
 
driverofLYN274 said:
Alright, here's what today yielded: the stator is consistent at 1.7 ohms on all 3 legs and all 3 have infinite resistance grounded against the frame......Thoughts?

Tom203: I'm not sure what you're referring to. My mystery wire perhaps?
Click to expand...
That 1.7 ohms is a little high, but could be meter having trouble with a low reading - can you try another meter?. Brown wire in headlight might have grounded out and blown fuse, but it shouldn't effect charging.I asked about the R/R because the older honda R/R's had a sense wire while newer units do not. As others have stressed, methodical checking of connections is a must.
 
Brown wire is tail-light/running-lights. Some bikes have a spare/loose connector in headlight shell.
Not related to your problem.


Stock GS does not have a scence wire, and if it did and if it were disconnected it would make the R/R go full out and you would have high voltage.

You measure the stator voltages yet?


PS: where in general are you located? Maybe add that in your user profile (goto UserCP), and maybe add your bike year model in signature line. Then those show up on every posting, makes it easier for folks trying to help.

.
 
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