250sx headlight only on with charger

[rzsox05]

The battery reads 12.5 v and at 1/2 - 3/4 throttle will reach 12.75v. When I turn the headlight on it does not light up and the neutral light goes off. It takes 2 -3 seconds for the neutral light to come back on once the headlight is turned off. If I hook up the battery charger 12v,2A the light works. Could this be as simple as the battery needing replaced? I thought since the battery was reading 12.5v it would be ok. The neutral light does the same thing when the starter button is pressed.

[atc500x]

Yes probably just need a new battery.

[85Tecate]

The battery is half dead at 12.5 volts. It should read 13.5-14v

[mmiguy2103]

The battery is half dead at 12.5 volts. It should read 13.5-14v

lol wrong.. the battery sounds fine at 12+ VDC. but when the bike is running it should read over 13VDC up to sometimes 15VDC depending on the condition of your bike. a fully charged battery is at 12.7VDC sounds to me like you have a chagrging issue not a battery issue. start by testing the regulator rectifier. specs are in the manual. than check your stator output voltage. and go from there.

you can also bring the battery to a local shop and have them do a load test to it. they will subject the battery to a very high amp draw and that will tell you exactly how the battery is feeling. alive or dead

[Coaltrain]

The hella 500 baja lights on my 250sx work just fine and I don't even have a battery in mine.

[rzsox05]

I tried testing the regulator. The values the manual says I should get are way off what I'm testing. With some connections I do not get any reading. I'll post the readings soon. I tried testing a spare (used) regulator and no luck. Any help will be appreciated.

[rzsox05]

I tested the regulator/rectifier the only wires I get a reading on are the green and black (30k ohms)within the limits(10-50k), all the other combos are open, I found the same on another rectifier I tested. The service manual says I should have readings b/w the G/Y,G/R, G/B, R/Y, B/Y wires. Is there a wrong way of testing these that could be giving me no reading?

The alternator exciter coil B/R and ground is 300 ohms (standard 50 - 200). This stator is from an 85 sx that I installed in my 86 sx last year. Would being 100 ohms over be enough to not charge the battery or headlight?

[rzsox05]

Does anyone have a suggestion for testing rectifiers/regualtors?

Any suggestions for getting a stator rewound. Ricky Stator said to contact a company called Custom Rewind. Has anyone used them?

[Dirtcrasher]

I can use 3 meters and get 3 readings................

From what I read on your 1st post, you have a bad ground or bad connection and make sure the alternator OHMS are in spec.

My battery is deader than my great great grandpa and my light works just fine. I can't buy a new batt every 2 years for an SX I don't use..........

[tri again]

84 br finally got a gas tank for it and for no reason now there is no spark.
Really dont wanna do a stator coil since I dont know if this bike shifts or has a rod knock or something else terminal yet

maybe I've lost my mind with this thing but....

if the stator puts out 200 watts of 12 volts, why couldn't we just use a low amp 12v power source like a battery to replace power from the stator just to see if it runs?

I hate to do a major tear-into if the engine or trans is no good.

[Dirtcrasher]

Like I said, a simple Ohmms test tells me if the light (Hi and Low) is good, but you can hook up a battery direct if you want to. Some batteries charge up to and over 13V so I'd only do it for a second....... Unless you put a VR inline with the battery.