Voltage regulator

[Denis]

I have a 1981 Yamaha xs400 special 2 and was wondering if I can get some advice on how to test my voltage regulator shown in the attachment.

Runs and rides perfectly ONCE started, but as of right now the lights don’t even come on when key is turned. Jumping it does the job and like I said runs perfectly just until I turn the bike off after a ride. Would love to hear what y’all think thank you in advanced

 

[avemachina]

Heya!

The headlight won't come on unless you start the engine; that's a design choice. The other lights... that's a different problem. I've attached the Haynes procedure for checking your regulator, but I don't think that's what's going on here--if you need a jump to start, I think your battery might be kaput.

The role of the regulator is to smooth out the alternator output, so that sort of implies that it's working correctly, since you said everything works once the bike's running (i.e., when the alternator is running).

If you've got a multimeter, make sure your battery is putting out at least 12.1V--mine won't even try to start if it has less than that.

 

[tstidham]

If the regulator is working correctly, you should see a little over battery voltage at idle (not much charging happening at such a low rpm) and over 13 to maybe 14.5 volts at 2k-5k rpms. When mine went bad, it only showed battery volts at any speed. The 1st replacement I put on showed normal volts until over 4k where it spiked over 16 volts. That's far to high and can start to damage things and boil over the battery.

 

[Denis]

Heya!

The headlight won't come on unless you start the engine; that's a design choice. The other lights... that's a different problem. I've attached the Haynes procedure for checking your regulator, but I don't think that's what's going on here--if you need a jump to start, I think your battery might be kaput.

The role of the regulator is to smooth out the alternator output, so that sort of implies that it's working correctly, since you said everything works once the bike's running (i.e., when the alternator is running).

If you've got a multimeter, make sure your battery is putting out at least 12.1V--mine won't even try to start if it has less than that.

100% was my battery, thanks dude