Charging system troubleshooting question

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RoadScholar said:
Integrated reg/rec units are readily available here in the states, as are 3 phase alternator kits. No good reason for paying high freight prices.

I have been told by sources that I trust that the new zenners that are currently available are not worth having. I made the assumption that the stand alone replacement rectifiers are of equal quality, I can't say for sure, but I'm not looking back in either case. Period zenners have 1/4-26 stud threads, available replacements are most likely to be M6 x 1.0; you can strip a 1/4-28 onto either, unfortunately.

If your wiring harness is the original you can start with breaking and cleaning ALL connections from the headlight to the tail light; this will, at least, buy your harness some time, but consider starting an escrow account for a new harness (while they last). Your switch gear would like their contacts cleaned and internal solder joints examined. There is absolutely nothing wrong with Lucas electrics; 40+ year old cars with original wiring have the same issues.

If this all gets too confusing PM me and I'll help you get this sorted.

Best.
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The shop manual shows a 1 ohm resistor in parallel with the VOM for doing the resistor test with the middle lead unplugged while on the cycle with the motor running. Is the resistor really needed? Doesn't the VOM (Fluke) have resistance built in it to prevent frying its voltage circuitry?
 
Arlen Johnson said:
Is the resistor really needed?
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Apparently not.

http://www.aoservices.co.uk/info/ALTERNATOR_COLOURS.pdf
"Full Output test

Now we have to be a little more electrically clever, do you have/can you use a multimeter? Have you got a friend who has/can? You need a 10AMP DC range on your meter. You do NOT need a 1 ohm resistor (Lucas suggestion). This test is the same for 6V and 12V and 3 Phase and High Output (with a little reservation we are coming to). Find the output terminal of the Rectifier or Regulator/rectifier. Disconnect its output lead. This might be a BROWN/BLUE wire and will be the Negative terminal if we have a Positive earth system. Connect the 10A DC meter between the output terminal and the wire you just pulled off of it. Lights on should NOT cause any current to flow, if it does then you’ve got the wrong wire (you might be on a battery lead). Start the bike, and put on all the lights. Rev up to 3000 or so and for the RM21 you should see close to 9amps. If you have some 3 phase or high output then you should pass the 10amps about 2500 revs."
 
Arlen Johnson said:
Back in 1960 or so, when I was a high-schooler with a Triumph TR6 Trophy, I heard about the British Whitworth thread system, but haven't thought much about it since. When you posted about the 1/4-26 thread on the Zeners I thought you must be mistaken. Fortunately, I didn't make an ass out of myself by saying you're wrong. Instead, I looked into it and...low and behold, there really is such a thing as a 1/4-26 thread...go figure. I intend to find and print a chart of all the British thread systems that were used then and now, and compare and contrast the various sizes. It turns out the 1/4-26 is in the British Standard Fine (BSF) system, not the British Standard Whitworth (BSW) system. It gets more involved because there are at least three more British thread standards: British Standard Cycle (BSC or BSCy), British Association (BA) and British Standard Pipe (BSP) All are mentioned in Wikipedia.
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It might be a mistake to miss out 1/4 x 26 tpi Cycle thread from the discussion.
 
Triton Thrasher said:
It might be a mistake to miss out 1/4 x 26 tpi Cycle thread from the discussion.
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As LAB said earlier you have 1/4 x 26 Tpi in brass (BSB) 55 Degrees and BSF at 60 degrees. I don't have in my hand a zenor but as the thread is brass I would think it is BSB rather than BSF.
 
L.A.B. said:
https://britishfasteners.com/threads/index.html
(BA page. Click BSC, BSF etc. for other thread charts.)



Edit: 1/4 CEI/BSC (60 Deg.) and BSB (55 Deg.) are also 26 tpi. :)
It says in the Wikipedia article that 1/4 BSF and BSC match which isn't entirely correct as BSF is a 55-degree thread although does mention BSC is 60 degrees in a note.
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Thanks for the link to the thread charts! They’ll save me a lot of time.
 
L.A.B. said:
Apparently not.

http://www.aoservices.co.uk/info/ALTERNATOR_COLOURS.pdf

Full Output test

Now we have to be a little more electrically clever, do you have/can you use a multimeter? Have you got a friend who has/can? You need a 10AMP DC range on your meter. You do NOT need a 1 ohm resistor (Lucas suggestion). This test is the same for 6V and 12V and 3 Phase and High Output (with a little reservation we are coming to). Find the output terminal of the Rectifier or Regulator/rectifier. Disconnect its output lead. This might be a BROWN/BLUE wire and will be the Negative terminal if we have a Positive earth system. Connect the 10A DC meter between the output terminal and the wire you just pulled off of it. Lights on should NOT cause any current to flow, if it does then you’ve got the wrong wire (you might be on a battery lead). Start the bike, and put on all the lights. Rev up to 3000 or so and for the RM21 you should see close to 9amps. If you have some 3 phase or high output then you should pass the 10amps about 2500 revs."
Click to expand...

Thanks! I understand and I'll do the test as soon as I get a chance. I'm retired, so I'm pretty busy. :)
 
Arlen Johnson said:
Thanks for the link to the thread charts! They’ll save me a lot of time.
Click to expand...

Many fasteners/threads on a Commando are Unified which you are probably more familiar with but they left some 'British' threads scattered about just to keep things interesting so if in doubt about a particular fastener then please ask.
 
L.A.B. said:
Apparently not.

http://www.aoservices.co.uk/info/ALTERNATOR_COLOURS.pdf
"Full Output test

Now we have to be a little more electrically clever, do you have/can you use a multimeter? Have you got a friend who has/can? You need a 10AMP DC range on your meter. You do NOT need a 1 ohm resistor (Lucas suggestion). This test is the same for 6V and 12V and 3 Phase and High Output (with a little reservation we are coming to). Find the output terminal of the Rectifier or Regulator/rectifier. Disconnect its output lead. This might be a BROWN/BLUE wire and will be the Negative terminal if we have a Positive earth system. Connect the 10A DC meter between the output terminal and the wire you just pulled off of it. Lights on should NOT cause any current to flow, if it does then you’ve got the wrong wire (you might be on a battery lead). Start the bike, and put on all the lights. Rev up to 3000 or so and for the RM21 you should see close to 9amps. If you have some 3 phase or high output then you should pass the 10amps about 2500 revs."
Click to expand...

I finally got around to doing your suggested test. I did the first part without starting the engine and here's what I found. With a nearly new, fully charged battery and all wires connected, (except the wires I tested on the rectifier), I get no current flow on any of the three terminals when I connect the Fluke VOM between one of the disconnected rectifier wires and the tab it was disconnected from, with the red cable of the VOM plugged into the 10A socket. I did the same test on each of the three rectifier terminals, one-at-a-time. There is no current flow with the ignition key off or on. The headlight stays dark with the ignition key off or on. Are these the results I should get?
 
Arlen Johnson said:
I finally got around to doing your suggested test. I did the first part without starting the engine and here's what I found. With a nearly new, fully charged battery and all wires connected, (except the wires I tested on the rectifier), I get no current flow on any of the three terminals when I connect the Fluke VOM between one of the disconnected rectifier wires and the tab it was disconnected from, with the red cable of the VOM plugged into the 10A socket. I did the same test on each of the three rectifier terminals, one-at-a-time. There is no current flow with the ignition key off or on. The headlight stays dark with the ignition key off or on. Are these the results I should get?
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Five minutes later...woops!, I see I did the above tests with the alternator wires disconnected from the bike's electrical wiring. I'll do the tests again and report back.
 
Arlen Johnson said:
Five minutes later...woops!, I see I did the above tests with the alternator wires disconnected from the bike's electrical wiring. I'll do the tests again and report back.
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I think you are ok with that part of the testing as you've already checked the stator and the rectifier so it's the second part you need to do now:


"Disconnect its output lead [rectifier]. This might be a BROWN/BLUE wire and will be the Negative terminal if we have a Positive earth system. Connect the 10A DC meter between the output terminal and the wire you just pulled off of it. Lights on should NOT cause any current to flow, if it does then you’ve got the wrong wire (you might be on a battery lead). Start the bike, and put on all the lights. Rev up to 3000 or so and for the RM21 you should see close to 9amps. If you have some 3 phase or high output then you should pass the 10amps about 2500 revs."

Output could be slightly higher for the RM23 as stated.

Edit:
There's also a test in the factory manual, section J, 'Testing the DC input to battery'.
 
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Arlen Johnson said:
Five minutes later...woops!, I see I did the above tests with the alternator wires disconnected from the bike's electrical wiring. I'll do the tests again and report back.
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I'm getting bummed out. Now the headlight doesn't work! The bulb passes the connectivity test, so I don't know what's going on.
 
Arlen Johnson said:
I'm getting bummed out. Now the headlight doesn't work! The bulb passes the connectivity test, so I don't know what's going on.
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If you still have those light duty mk3 white plastic connectors , they might need attention ( or removal)
 
L.A.B. said:
I think you are ok with that part of the testing as you've already checked the stator and the rectifier so it's the second part you need to do now:


"Disconnect its output lead [rectifier]. This might be a BROWN/BLUE wire and will be the Negative terminal if we have a Positive earth system. Connect the 10A DC meter between the output terminal and the wire you just pulled off of it. Lights on should NOT cause any current to flow, if it does then you’ve got the wrong wire (you might be on a battery lead). Start the bike, and put on all the lights. Rev up to 3000 or so and for the RM21 you should see close to 9amps. If you have some 3 phase or high output then you should pass the 10amps about 2500 revs."

Output could be slightly higher for the RM23 as stated.

Edit:
There's also a test in the factory manual, section J, 'Testing the DC input to battery'.
Click to expand...

Here's what I get when I do the test with engine running. BTW, the center rectifier connection IS the BROWN/BLUE wire. OK, at 1000 RPM it's only about 0.4 amps DC current. At 3000 it's 1.1 amps.
 
Arlen Johnson said:
Here's what I get when I do the test with engine running. BTW, the center rectifier connection IS the BROWN/BLUE wire. OK, at 1000 RPM it's only about 0.4 amps DC current. At 3000 it's 1.1 amps.
Click to expand...

Seems low, but as my Commando isn't exactly in one piece at the moment I can't say for sure, although I would expect the test information in the AO Services pdf document to be accurate.
 
Just thinking (guessing!). The AO test might not be suitable for the 850 Mk3 with twin 'AC' Zeners.

I suggest you try the 'DC input to battery test' as described in the manual!
 
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The ammeter connection between the 'battery negative terminal' and the 'cable' mentioned in the test should be the brown/blue harness wire, not the starter motor cable or don't use the electric starter.
 
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