Re: Is my regulator no good ??

Posted by sgtslag on May 11, 2012; 4:21pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Is-my-regulator-no-good-tp3973039p3980408.html

Voltage runs through a circuit, like water through a pipe.  With voltage, it has to be a closed system to flow.  That means that voltage flows from the negative terminal of the battery, to the positive terminal, literally (electron flow).  So, yes, there will be voltage on the negative terminal, but it depends on how you are measuring.  Circuit "Ground" is a reference point; it could be the positive terminal of the battery, or the negative terminal, but the negative terminal is usually used as the common, "Ground" point, from which all voltages are measured (black voltmeter lead goes here, red lead wherever you wish to measure for voltage).

Voltage is actually a measure of pressure difference:  12 Volts of pressure, is measured between the positive battery terminal, and the negative battery terminal.  If you measure between either battery terminal, and a cold water pipe (literally, Earth Ground), you will measure 0 Volts (not a complete circuit, unless you connect one of the battery's terminals to a grounding rod).  Earth Ground, and circuit ground, are not the same, but they can be -- if your circuit ground (reference point for making voltage measurements) is connected to the Earth Ground.  On vehicles, Earth Ground is not connected, so all "Ground" references, are only for that circuit, which happens to be the Negative terminal of the battery -- it is only a reference point.  If you put the black voltmeter lead somewhere else (other than circuit ground), you may see voltage present, but it may not be a fault (known are a "voltage drop", which is beyond this discussion).

Connecting a battery to the AC input on the Rectifier/Regulator input will supply voltage to the output side of the Regulator, but it is not a recommended method of testing/troubleshooting.  Without getting into the Bridge Rectifier circuit details, I would not recommend it.  Try what I wrote before, about using a 30 Amp, in-line fuse between the battery's Positive terminal, and the bike's Positive battery cable.  This will be much easier to test, and troubleshoot.  Once you get the bike wired up, you can then test the Rectifier/Regulator in a straightforward manner.

To test the Rectifier/Regulator, start the bike.  Place a voltmeter across the battery terminals.  Run the engine at ~2500 RPM:  the voltmeter should read somewhere between 13+ to ~15.5 Volts.  This will tell you two things:  1)  the alternator is pumping out AC, more power than the bike is consuming, which is charging the battery; 2)  the Regulator circuit is keeping the voltage from getting too high, preventing it from damaging the bike's electricals, and from destroying the battery, itself.

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Basically, you can ignore the explanation on how electricity, and Ground connections work, and just hook up the battery with the in-line fuse, for testing.  Make all voltage measurements only with the black lead connected to the Negative battery terminal.  Anything else (black lead somewhere other than the Negative battery terminal) is just a Voltage Drop measurement, and it won't help you.  Cheers!