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stator papers R/R testing diodes FYI

  • Thread starter Thread starter Tom108
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Tom108

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FYI- In the stator papers II how to test your regulator/rectifier, it should specify- to use a Voltmeter(VOM) with the (diode test function), not just the regular ohm setting because the test will not work on that setting. The Diode test symbol is a small arrowhead with the point of the arrow touching a short vertical line. You will need to set the dial to this setting. When the test is performed correctly you will get a reading, (mine was around .600) in one direction, when the leads are reversed, you get a small L or other depending on your particular VOM meter. I have seen quite a few posts regarding this issue it seems to have caused a lot of confusion (myself included) hope this helps others a little. Tom108
 
Good clarification, but it is possible to do the test either way. If you want to use resistance or you don't have a digital meter with a diode test, set the meter to the 10K or 20K scale (depending on what your meter has). Forward biased (positive lead on the anode and negative lead on the cathode, you should get a reading somewhere between 1K and 2K. Mine actually read about 1.3K. Reverse biased (positive lead on the cathode and negative lead on the anode) you should get essentially infinite resistance. If you are measuring the diodes that have one end connected to ground, the anode is the side that is connected to ground and the cathode is the side that is connected to the stator. If you are measuring the diodes that have one end connected to the red wire going to the battery, the anode is the side that is connected to the stator and the cathode is the side that is connected to the red wire.
 
tomm- I just tried to test two different R/R's on the OHM setting at 20k with two different digital VOM's using the method you describe, still got no readings, maybe you are doing something different. Maybe you are using an analog type unit? These are R/R's from a 1982 GS550L. Maybe some of the R/R's have a different design which allows them to be tested using just an ohmmeter?
 
Tom108 said:
tomm- I just tried to test two different R/R's on the OHM setting at 20k with two different digital VOM's using the method you describe, still got no readings, maybe you are doing something different. Maybe you are using an analog type unit? These are R/R's from a 1982 GS550L. Maybe some of the R/R's have a different design which allows them to be tested using just an ohmmeter?
Click to expand...
Analog is what he's referring to in his post...
 
The method I described is the typical analog method for checking a diode, but it should work with a digital meter as well. These meters measure resistance by putting a voltage across whatever it is you are trying to test, and then measuring the current flow. The meter can then determine the resistance from Ohm's Law . . . Resistance = Voltage / Current. Since a silicon diode forward biases at between 0.6 and 0.7 volts, any meter, digital or analog, that puts that voltage across it would forward bias it, current would flow, and you would therefore read a finite resistance.
If that isn't what you are seeing, you either have bad rectifiers or there is something wrong with your meter. You might want to check to make sure the battery isn't dead in the meter. That's what supplies the voltage to put across whatever it is you are trying to test. Second possibility is that you might have accidentally tried to measure the resistance of an active circuit. Quick way to blow the meter.
I'm not familiar with your bike, but I can't really think of anything different in the rectifier that would account for what you are seeing. Rectifier circuitry is pretty standard stuff.
I happened to be doing some testing of my own charging system last week, and used a digital meter to check the diodes. Worked as I described earlier.
 
I did the test using two different meters, on the bench, with two different R/R's, Both meters zero and the displays seem normal, I have an analog meter at home will try that also.
 
Not sure what you mean by "both meters zero". Are you saying that when you measure the resistance across the diodes in either direction, you are getting a reading of zero, or a reading of open, however your meter indicates that. Mine shows a 1 for open circuits, usually 0.004 for dead shorts, and something in between for everything else. Or that both meters are zero-adjusted.
And I'm sorry, but I have to ask, you have one probe on one of the leads that the stator connects to and the other probe on either the black wire that goes to ground or the red wire that goes to the battery, right? Then you are reversing those probes. And then moving to the next wire that the stator connects to and repeating the same two measurements? And finally to the last wire that the stator connects to? So six measurement in total. What is your meter showing for each of these when on the 20K scale?
 
you have to have a diode test function on a digital meter to get proper readings. analog meters almost never have this function.

a good test will show approx. .450 forward bias and OL in the reverse (open line)
 
A digital meter without the diode test function will still be able to test the diodes using resistance. There should be a relatively low resistance (1k or so) in one direction, basically infinite resistance in the other direction. Note that this will only test for open or shorted diodes.

The advantage of the diode function is that it applies enough voltage in the test circuit to turn the diode ON. It then displays the turn-on voltage. Most of the r/r that I have tested show this number as about .450 or so.


.
 
I meant "zero" when you touch the probes together when you initialize or check them before taking a resistance measurement like on the old analog meters. I finally did get a reading on one of the meters on the 2000 ohm scale but not on the 20K scale, and still nothing on the other meter. But both meters worked fine in the diode test position. I don't know why they don't work in the regular ohm position, maybe they're just cheapo meters and don't perform like they should. I did notice that a lot of posters were wondering why their ohmmeters didn't get any readings during this R/R test though. Probably worth the investment to get a good quality VOM.
 
I was using the procedure for R/R testing in the stator papers II, the chart that shows each wire (y,W/B,W/R,B/W)tested to red and then test leads reversed. And then the three stator wires (Y,W/B,W/R) tested to B/W, and then test leads reversed. These are with the R/R's on the bench, off the bike.
 
tomm said:
Not sure what you mean by "both meters zero".
I meant they both initialize and read zero when the probes are touched together, before any measurements are taken.
Are you saying that when you measure the resistance across the diodes in either direction, you are getting a reading of zero, or a reading of open, however your meter indicates that.
A reading of OPEN. Yes it's a one(1)
Mine shows a 1 for open circuits, usually 0.004 for dead shorts, and something in between for everything else. Or that both meters are zero-adjusted.
Both meters are zero adjusted that's what I meant.
And I'm sorry, but I have to ask, you have one probe on one of the leads that the stator connects to and the other probe on either the black wire that goes to ground or the red wire that goes to the battery, right?
Yes, I was following the test procedure chart for R/R's in the stator papers II.

Then you are reversing those probes. And then moving to the next wire that the stator connects to and repeating the same two measurements? And finally to the last wire that the stator connects to? So six measurement in total. Actually it's seven times two= fourteen measurements.

What is your meter showing for each of these when on the 20K scale?
A reading of open (1).
Click to expand...
Both meters work fine in the diode test position, but not in the regular resistance (ohm) setting 2k, 20k.
 
My mistake on the 6 measurements. Should be 12. Two measurements across each of the 6 diodes. What are you measuring for the other two to come up with 14?

Guess I'm not sure what to tell you about what you're measurements are though. A silicon diode fully forwards biases around 0.6 or 0.7 volts, and usually presents a resistance of around 1.3K to 1.5K. Reverse biased, it should show as infinite. And either a digital or analog meter should be able to take those measurements.

If you have a digital meter and use the diode tester, you can as Steve said, see at what voltage the diode turns on. And it is a perfectly acceptable way to test. But both a digital and an analog meter will turn the diode on.

Personally, I prefer the analog meter for this type of testing, and use the digital meter mostly for very low resistance measurements, like the stator windings, where the analog meters can be a little hard to read and even a little variance can be bad. But I typically don't like things that tell me good / bad. I'd just as well know what the measurement is and then decide what it means for myself.
 
And the final answer is: It depends, you will have to read the manual for your meter ...

I just checked two of my cheapy digital meters and the results were:

meter one - only worked on diode function.

meter two -
range
200 ohm - brief indication then infinite
2000/diode - (the same range setting is used for both) works as expected
20k, 200k, 2meg - doesn't work
20 meg - works again ... (huh ... wierd)

The short answer is that the readings should be consistent for all the diodes, but the correct setting can depend on your meter

Oh, and BTW, which lead (red or black) should be which can also vary between meters, as long as all the diodes read roughly the same (and there is a difference between directions), you are probably good.
 
tomm- The last measurement on the R/R is between the Red wire and the black/white(ground) wire so I guess there's another diode in there between those and it reads a little higher around (.940) on the diode tester, and (1) in the other direction(over range is what the manual calls a 1) with leads reversed. So it's a total of 14 measurements 7 each way. It's exactly what's shown in the "stator papers II".
 
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.
 
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.
 
tomm said:
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.
Click to expand...

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.
 
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.
 
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