Headlight Not Working, What Voltage should I be Getting?

[tom4130]

Hi Everyone.

So I am nearing the completion of my build, and noticed that the headlight is not working when the bike is running. I have a '80 xs650 special.

Now this may seem like a silly question, but I am not sure how to test whether or not it is the headlight thats not working or my wiring, as I still have the headlight safety relay in the harness.

Should my headlight be coming on when i turn the key, before I start the bike? If not, are there any checks I can do with a multimeter to see if it is the bulb, or the wiring thats the problem?

Also is the answer to bypass the safety relay to make this check. If so what is the easiest way to do that?

So close but yet so far! Thanks for any answers.

 

[gggGary]

Start by using a volt meter to see if the charging system is working. With a good battery and working alternator, one good strong kick is enough to close and latch the headlight relay and light the bulb even if the engine doesn't start. Once the headlight comes on, the relay holds in even if the alternator quits, until the key is shut off.

Some plowing of this field

and here

 

[XSLeo]

To add to what gggGary said, no, the headlight does not come on with the key. It comes on after the engine starts. It will as gggGary said come on if kicking, even if the engine doesn't start.
The way the safety relay/headlight relay works is that when you turn on the key the safety/headlight relay lets power flow to the starter but not the headlight. As the engine starts the alternator starts to put out voltage. Some of this voltage is taken on the yellow wire to the safety/headlight relay. As the engine starts the voltage increases, when it reaches about 4.5 volts the relay trips and shuts of the power to the starter and sends power to the head light.
So as gggGary said you need to check the battery voltage. It should read somewhere around 12.5 to 13.5 at idle. If lower your charging system need work.
Leo

 

[tom4130]

Thanks for the advice guys, Turns out I am a moron and it was blown fuses that were the problem!

Both of you thanks for a little more clarification as to what the Safety Relay does