Why is my voltage reading bouncing around like crazy?

I have a 71 Kaw enduro with a magneto and 6v system. The battery charges ok, signals work etc. My headlight won't work, so naturally I went to check the voltage and the numbers on the meter are just scrambled, bouncing wildly and never stopping long enough for me to even read one. I tried another meter and same issue. Doesn't matter if I select AC or D.C. volts and it does it on all meter ranges. I know the meter works because it reads 6.5v at the battery and works with my other electronics projects. I've tried checking both low and high beams, grounded to both the headlight ground and the frame.

The headlight has its own coil. It is not rectified or regulated, so I suspect my issue is that the power coming from that coil is just very poor quality AC. However, what can I do to fix that? I have an aftermarket regulator on the coil that charges the battery, but before I drop another $25 for another one I want to make sure that's my issue.

This is the wiring diagram for the bike.




Thanks in advance.


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Since your alternator is making AC current, you need a rectifier to convert the AC to DC. I would imagine that you would need a regulator, too, so that the light doesn't fluctuate with low/high RPM. You can probably find a working regulator/rectifier on Ebay for an older 6v system dirt bike for pretty cheap. Hope that helps

interceptor said:

Since your alternator is making AC current, you need a rectifier to convert the AC to DC. I would imagine that you would need a regulator, too, so that the light doesn't fluctuate with low/high RPM. You can probably find a working regulator/rectifier on Ebay for an older 6v system dirt bike for pretty cheap. Hope that helps

Click to expand...

It does, thank you. There's some up there that are new for $16. I'm gonna scope it out. Thanks!


Here's where I list all my bikes:
'71 Kaw 250 Bison
'81 KZ750 cafe
'94 XR250L
2014 Yamaha Bolt

In progress: '68 CL350