Topic: Voltage Regulator sanity check.

[TwoTired]

If those readings were at the connection points to the Vreg, I'd say it isn't showing a problem there with those readings.

However, it would be a more interesting data point to add, if those readings were taken while the charging system was in suspected failure mode.

Good reading while working is ok.
Good reading while the system fails means another component bear scrutiny.

Didi you discover why you were reading 9V at the Black wire?  That's an issue to solve.

[Rgconner]

9V issue is likely my issue. Checked it again today, took 3 readings, and it is 11.3 V, slightly lower than the reading at the battery of 11.7 when the key is on. I recleaned things along way, anything I removed got a surface cleaning, including bolts and where they went into the frame. Hondaman has pointed out that these can cause issues if the ground to frame becomes dirty.

Ran it out on 20 mile ride each way, outbound was no headlight, voltage at battery after letting it settle was 12.65v.

Ran it back with headlight back on, voltage at Battery was 12.5V.

It seems to be working for now at least, I will have to keep an eye on it.

[TwoTired]

Did you know you can use a voltmeter to see the differential between source and destination?
One probe on the battery post and the other on the black wire will tell you the loss between those points.

You can use this same technique to measure "across" devices in the path to find the significant contributor to the loss.

High resistance connections lose more power when the current load is increased.  If a device loses 1 volt and mid load, it can show more of a loss when the the current is increased through it.  (Think headlight on or headlight off.)

Cheers,