250sx electrical question

[Deere]

On my 85 250sx, I noticed that the battery wasn't staying up. it's new.

On testing the voltage at battery at running/lights on etc, there is no change in voltage when revving. OK so I check the output of the stator on AC and I can see it climbing and trailing when revving, so stator must be working.

Start the bike on no battery, kick start, and it runs fine, but no lights of any kind.

Obviously stator keeps electricity to fire the coil and CDI unit. I unplugged the stator when running and as expected bike dies.

So I suspect bad rectifier as AC output is not gonna light nothing. Any other test besides what I've done to confirm?

Thank you!!

[Deere]

OK, I'm posting as I found the problem and thought I'd share this, as I bet someone else had this problem

When I got the bike, the red hot wire from the positive side of the battery, goes into the harness spliced into the rectifier plug and then goes up to the ignition switch. Someone had bypassed it and went right from the battery to the ignition switch, as the PO thought that it was the way to fix it. The reason was for doing so, was that the hot was lost in the harness after the recitifier.
The bike ran fine, but no charging, and no lights with no battery. Well after scratching my head, and reading the book, the recifier plug should have 12v when the switch is off. It did not. I found that the factory splice, which is about an inch up the main harness from the rectifier plug was broke. I repaired it, and then spliced in the new wire going to the ignition switch, so now the plug is hot, and the ignition is hot. It makes sense, how else would the rectified AC get back to the battery and circuit?
So then I went to button it back up, and then found that I had no neutral light, and no electric starter. ARRRGH. The solution was that the neutral and reverse connector on the block was loose. When this is not connected, the rest of the circuit to the electric start is no longer hot, and grounds out the ignition.

I bet this is a common problem, this splice in the harness. Hopefully this will help someone else. Its a PIA to unwrap and discover.

Fired it up, and now all works as it should. Charges, and lights when no battery is connected!!!

[Frankencelery]

Now here's a guy I can relate to. Owns a 250SX, and answers his own posts! There's entire posts on here where it's just me talking to myself, working out one problem or another. I can only hope that more people find them helpful than people who think I'm a moron! But seriously, thanks for posting what you found, it could be something that happens to mine someday.

[tri again]

Nice work!

I have a handful of sx's and actually have heard about a bad wire/connection near the battery but I haven't seen your post until this minute.

The neutral switch connector on the bottom of the block is not uncommon.
I think I found a new switch for 12$ locally.

Sometimes just writing stuff down will get you your answers too.

[atc007]

Great work Deere! I haven't seen that one! Would have had to work awhile to have figured this one out. Thanx!!

[Deere]

Thanks fellas. Iwanted to share, because I've seen hundreds of posts on other boards where no one is talking, or the person fixes it, and never tells what they did.

I did a search on this in the forums, and didn't come up with much.....

So to summarize, anywhere there is a connector in the wiring diagram, that's where to start looking. Testing ohms connectivity and 12 volt sensing is the ticket to figure it out. The hot red wire goes into the harness at the rear from the battery, and then the rectifier plug is splices on to it, and it continues to the ignition switch. When I got to the splice, it literally disintegrated. I was really surprised. Now You all know what I know