yamaha alternator trouble shooting

[thomak]

The alternator on my XJ 650 seca isn't working. Also my headlight isn't working. I believe its the same trouble because the headlight relay's power is connected to the output of the voltage regulator. I don't have a manual for this bike, so I don't really know where to start. I downloaded a wiring diagram and did some trouble shooting of my own but didn't get anywhere. If anyone has any ideas that would be great. Thanks.

[Sev]

How do you know the alternator isn't working? I'd check the fuses, and the bulb first - kiss and all that.

First things first you gotta check to see if there's any output from the alternator, start the bike, check the voltage across the battery at idle, then at 5000rpm. It should be at least 13 volts, and should increase with rpm rise.

If it doesn't you need to look for the three yellow wires leading from the alternator, set your multimeter to ac voltage. Disconnect the three wires, and run the bike with it disconnected. Now you need to check across all three wires in all combinations:

AB
BC
CA

All of them should be about equal in output. If one is substantially lower you've identified a bad coil.

[thomak]

The fuses are all good along with the bulb. I checked the continutity through both filaments. The volatage of the battery goes down after I start the bike and rev it up. It never goes above maybe 12.2 and drops as low as 11.9. I'm pretty sure it an alternator thing.

I'll check those wires. Any idea what the AC volatage should be. or should I just look for consistancy?

Also does it make sense that the headlight relay would be connected to the output of the alternator. It seems a little wierd to me but from the wiring diagram that I have it looks like thats whats happening, so I am hoping that the two problems are really the same.

Thanks for your advise I'll keep you posted on what happens.

[thomak]

So no luck with the alternator. It still may be winding issues, but I'm not so sure because I have a parts bike for it, and both the windings are reading the same resitance. I have switched the outer winding because that was easy to do, and it made no difference. Both the inner windings are reading 5 ohms of resistance. ( I don't know if this is what it should be but since they are both the same I figure it must be pretty close to good.) Voltage is comming into the inner winding but only 196 millivolts of current. I have switched the voltage regulator and that made no difference either. I'm just at a total loss as to what could possibly be wrong. Thats the trouble I guess with old motorcycles that you didn't pay much for.

[Sev]

Yeah, sounds like your charging system is pooched. You're running off battery power only right now. I cannot off the top of my head recall what the output should be, but you're going to want to check regardless. If the output there is good it's possible that regulator/recitifier went. We'll wait and see what happens with the alternator output.

[thomak]

So after all this troubles and thinking that my alternator was all messed up. or who knows what. Last night I realized that when I had the motor out of this bike I connected two connectors backwards. The alternator connector was going to the ignition relay and the kickstand switch to the alternator. I'm not sure how I missed this dumb mistake considering I have spent hours and hours pouring over the bike looking for somthing that was wrong but last night at 10 I finally noticed the colors didn't match up on the connectors. Everything is now working and I'm gunna take my first ride after school today.

Thanks a lot SEV for helping me through this at the very least I learned a lot about the wiring of my bike.

[Sev]

That sucks and is awsome at the same time. Grats on getting everything sorted at least.