stator papers R/R testing diodes FYI

[smagnusen]

My 7-wire honda R/R replacement did not show any readings for two out of the three stator paper tests. However, the R/R seems to be working well. I've put some miles on it since the installation and the charging voltage is on spec.

My assumption is that the electronics are different and the stator test is not applicable.

[tomm]

I wouldn't assume the stator papers don't apply and that the electronics are different. These circuits are pretty standard. And as bakalorz indicated earlier, meters can sometimes give misleading results. That's why good meters cost hundreds, and the ones we use all the time cost 19.99.

Give or take, the charging system looks something like the attached figure. The rectifier and regulator may be one unit or two. In the early GS'es, one of the stator leads goes through the light switch before connecting to the rectifier, and I believe only one rectifier output went to the regulator. And there may be a sense wire that helps control the overflow current (not shown in this picture). But those are more variations in implementation than they are in design, except maybe the sense wire.

I've never seen the inside of a Honda 7-wire R&R, but I'd be really surprised if it is fundamentally the circuit shown, same as the OEM setup and same as the Electrosport replacement. (The problem with the OEM circuit isn't so much the circuit as the way they decided to connect the pieces and the quality of the design . . . heat sinking, ruggedness of components, etc.) And the Electrosport doesn't have the separate sense wire. It senses the rectifier output directly.

[smagnusen]

I wouldn't assume the stator papers don't apply and that the electronics are different. These circuits are pretty standard. And as bakalorz indicated earlier, meters can sometimes give misleading results. That's why good meters cost hundreds, and the ones we use all the time cost 19.99.

Give or take, the charging system looks something like the attached figure. The rectifier and regulator may be one unit or two. In the early GS'es, one of the stator leads goes through the light switch before connecting to the rectifier, and I believe only one rectifier output went to the regulator. And there may be a sense wire that helps control the overflow current (not shown in this picture). But those are more variations in implementation than they are in design, except maybe the sense wire.

I've never seen the inside of a Honda 7-wire R&R, but I'd be really surprised if it is fundamentally the circuit shown, same as the OEM setup and same as the Electrosport replacement. (The problem with the OEM circuit isn't so much the circuit as the way they decided to connect the pieces and the quality of the design . . . heat sinking, ruggedness of components, etc.) And the Electrosport doesn't have the separate sense wire. It senses the rectifier output directly.

I agree, mostly. Just a couple additional thoughts. My diode tester was indeed a cheapo unit, though it does work in other applications. It seems not to matter though, if it's a fault with a diode or it's a fault in the diode tester, that as you say, most people use. Either way, it renders the test useless. If the cheapo diode testers are likely to give inaccurate results, then it would be a mistake to conclusively diagnose an R/R with one. Better to try the R/R as I did.

Also, I actually wouldn't be suprised if modern R/R included secondary circuits (for protection or whatever) that might keep the diodes from being tested via the stator papers method. Then again, my electronic knowledge is limited.

[tomm]

There is some really good information on this subject at the following link.

http://www.allaboutcircuits.com/vol_3/chpt_3/4.html

The standard GS circuit is the 3-phase AC source setup. Not much has changed in these designs over the years.

The info under 'Meter Check of a Diode' also has good info in it about why meters sometimes don't give the expected readings. And diode test measurements vs. resistance test measurements. The info here is really important to make sure you're tests are meaningful.

Finally, the info under zener diodes helps to explain how the regulator works. Unlike rectifiers, which are all pretty basic in design, the same can't be said about regulators. However, vehicle regulators are all pretty similar now. (Early car ones used to be mechanical.) Some may use SCR's (silicon controlled rectifiers) instead of zener's etc, or may use the zener as a gate. So these can be pretty hard to measure out without really knowing what's inside. But they all have some way to detect rising voltage and siphon off excess current to ground Fortunately however, when regulators fail, it's pretty obvious by looking at the battery voltage as your electrolyte boils away. Interestingly, when zener's fail, they usually fail short.

I wouldn't write off testing as useless or blame the test equipment. Just important to understand how your meter works, what you're measuring, and how, so that you know how to interpret the results. It should be possible to check a diode with any meter in some fashion.

Coming to the right answer often involves putting together all the facts, not just taking a single measurement and going with it. And that includes common sense observation about whether everything seems to be working OK, are there hot spots, connections burning, lights dimming, directionals not blinking, etc.