Re: Regulator, how does it break?

Posted by sgtslag on Mar 28, 2012; 8:44pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Regulator-how-does-it-break-tp3865650p3865917.html

Actually, it is a bit more complex.  The Rectifier converts AC into DC (uses solid state diodes:  they can get hot from the current running through them, which is why the whole assembly has a heat sink attached to it -- aluminum fins for cooling; excessive heat will burn them either into an open circuit, or a short circuit -- both are a critical failure).  The Regulator is a separate circuit, physically attached to the Rectifier circuit assembly; the purpose of the Regulator is to shunt excess voltage to the bike's circuit ground (back to the Alternator), to maintain the voltage (electrical pressure, similar to water pressure) at a safe level -- typically less than 15 Volts.

The Rectifier, and the Regulator are put into one assembly to take advantage of using one heat sink for both, and to conserve space on the bike's chassis.  They're electrically separate circuits, but inter-related.  They're designed for heavy duty, but the safety margin is only so big.  With age, silicon junctions (diodes, transistors, and other components) fail; heat cycles stress them, which also leads to failure.

I have not replaced mine yet, but here is a site I keep bookmarked, should I need to replace mine:

http://www.oregonmotorcycleparts.com/Reg_rec_units.html

He claims his parts are over-engineered, so they have a larger-than-OEM safety margin.  That is a very good thing.  If mine goes, I plan on ordering his unit, not an OEM.  Many advances have been made in solid state electronics since your bike was built, and mine ('79).  Today's diodes, and other silicon devices, can handle more power, in smaller packages.

As far as testing the Rectifier/Regulator goes, it can be done with a Digital Multimeter costing as little as $5-$10.  The instructions on how to test it, are in the FSM, available off of the Home Page of this site.  To test whether your Rectifier/Regulator is working properly, just connect a voltmeter across the battery terminals with the bike running, and open the throttle to achieve 2,000 RPM:  the voltage should read 14+ Volts, if the Rectifier/Regulator is working; if it reads less than 13 Volts, the battery is not being charged, and the Rectifier/Regulator is not working, or the Alternator is not working.  Set your Digital Voltmeter to A/C, and connect the leads across two of the yellow wires, attached to the Rectifier/Regulator (A/C lines from the Alternator):  if you read more than probably 6 VAC (the correct value is unknown to me, as it is a three-phase AC output, so the A/C voltage may be higher), the Alternator is working, if it reads less, or zero, then your Alternator is NOT working (see FSM for troubleshooting methods).  Cheers!