Mk3 WLA, Alternator, Rectifier, Zeners, battery

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still running, switch key to headlight lo beam and ammeter starts swinging plus 6 then minus 6 amps every second. tick tock while revs at 3000rpm. the swinging is so pulsing that I cant really tell what the actual reading is .

that's what happens when your directional indicator is ON. The pulses of the blinker cause wild swings of the current and it's reflected in the ammeter.

If the directional switch is OFF and you are getting that ammeter reading then you've found at least one issue. Your directional circuit has a short in it.

If you've just inadvertantly left the directional ON, then turn it off and you should see slightly negative ammeter reading below 2000-ish RPM's, and the ammeter should tilt into the positive above 2000 RPM's, but not go much past "slightly charging" on the scale because the zener converts extra current into heat. If it's charging excessively, then either your battery is very low, and it's accepting a heavier current OR your zener is toast.
 
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I would start by installing the correct voltage battery.
Nobody that runs a Li battery believes they are wrong for an old charging system, until problems show up.
It's now a disclaimer on the Shorai site
" Do not install these batteries in a vehicle with a charging system that produces less than 13.1 volts at idle"
Pretty much every old Brit bike produces less than 13.1 volts at idle. Some barely manage that at speed!

I met another fellow on the weekend who just installed a new Alton , Podtronics and Shorai on his old Brit bike. He thought the Shorai was about the coolest bit of technology ever invented.
I tried to explain that what he has is a mismatch of technology and that bad things will occur, but he would have none of it, thought I was talking thru my hat!

Glen
 
New data today,
Key in "run"...... pilot light , red light, green light ,taillight, ignition are on.
Electric start , engine running ..
at idle amp needle moves slightly to chg, maybe half needle
increase to 2000 rpm, needle moves to maybe 1amp
3000 rpm, needle moves to 2amp
4000rpm, maybe 3 amp

turn ignition switch to headlight, lo beam H4, while still running
at idle needle is at minus 6amps
2000rpm , needle at minus 3amps
3000rpm, needle at minus 1amp
4000rpm, needle is at zero amp

red light , WLA, on dash does not dim anymore, simply stays bright .
new H4 headlight does not come on in "run".
The old headlight did come on in "run" and dim/bright with rpm.

Li Shorai LFX18A1-BS12 battery voltage check, with all off after todays run, 13.5v
 
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Your H4 is drawing 12.8vx6A=75 watts
I still think it killed the HCU output transistor that runs the head lamp, but did not affect the tiny red indicator transistor.
Try putting a low wattage bulb on the HCU out put, but I doubt you will get any glow.
If you buy another HCU, you better isolate the HL with a relay or better yet put a series current limiting resistor for daytime running or you will kill it again.
 
I agree the new H4 seems to have killed my WLA.

I did get suitable dimming of the red light with OEM headlight for 1000miles, then the WLA/HCU red light would only partially dim.
did I loose a zener?
did I loose one leg of alt?
did I loose rectifier on side?
 
Can I unplug a zener and test one alternator side at a time?
Maybe the rectifier as well , matching the zener?
 
My judgment is the original Mk3 electrical system was working fine for 1000 miles. Then something electrical failed to only allow partial charge, and this was indicated by the red warning light not fading away as original, but just slightly fading.
My riding was daytime, no night riding, no slow speed city riding, but this original Canadian headlight was fading lo/hi with RPM.
Then I installed an H4 bulb to brighten headlight and the WLA/HCU failed after working (fading) one time.

But ......these current ammeter checks show the charging system still capable of partial charging.
So, I would like to determine if my suspected failure is a zener, the rectifier, or one leg of the stator.

If my Mk3 is running on the work stand, can I disconnect a zener without blowing the stator and learn if one side is not producing?
Or is there a better test method?


Mk3 WLA, Alternator, Rectifier, Zeners, battery
 
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I had a "partial charge" situation, it turns out that one diode in the rectifier had a broken connection.
Replaced rectifier, all fixed. Rectifier can be checked with an ohm meter or continuity light. Check each combination of connections. Current should flow one direction, reversing test leads should be no current flow.
 
The Commando workshop manual has test procedures for the electrical components. Rectifier is tested with an ohmmeter, zeners are tested with an ammeter and voltmeter. Each zener could be tested separately. Basically, you look for the voltage at which the zener starts conducting.

Is there an online workshop manual, or at least a schematic, for the MK 3?
 
I had a "partial charge" situation, it turns out that one diode in the rectifier had a broken connection.
Replaced rectifier, all fixed. Rectifier can be checked with an ohm meter or continuity light. Check each combination of connections. Current should flow one direction, reversing test leads should be no current flow.

I had exactly the same condition on my bike once. With an analog Boyer the idle changed when a blinker was on - battery was too low. Good thing it was day time.
 
removed Mk3 rectifier, using oem Mk3 headlight and 12v agm battery tested rectifier, rectifier tested good.

Reinstalled rectifier dated 7450.

Mk3 WLA, Alternator, Rectifier, Zeners, battery
 
In reading the workshop manual, it appears it would be okay to disconnect one zener at a time and not affect the stator.


Mk3 WLA, Alternator, Rectifier, Zeners, battery

if I did so, and then run the above test at rpm, and something changes , perhaps this would indicate a faulty side of the stator, eh?

Maybe I could put a voltmeter on the disconnected zener feed and see if there is voltage, eh?
 
Test zeners one at a time without revving too high but make or break connections with engine off. Don't just yank off the wires while engine running.
 
So I pulled one zener off at a time, elec started Mk3 bike, key on "run" .....
(with key in "run", green light, red light, pilot light, taillight, ignition are on amps show neg 1 amp.)
at idle amps were neutral/0 amps
rev to 4000, amps went linear to 10 amps = 2000rpm=5 amps.
both zeners tested same, but H4 headlight wasn't on .

turned key switch to lo beam H4 headlight, instant minus 7 amps, either zener unplugged, and the revs struggled to achieve 0 amps, 4000rpm = 0 amps

plug zeners both back in and results are same as above.

I am not sure what this tells me.....but the stator must be doing some charging
 
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New data today,
Key in "run"...... pilot light , red light, green light ,taillight, ignition are on.
Electric start , engine running ..
at idle amp needle moves slightly to chg, maybe half needle
increase to 2000 rpm, needle moves to maybe 1amp
3000 rpm, needle moves to 2amp
4000rpm, maybe 3 amp

That ammeter behavior sounds normal and I've run an ammeter for a few decades. There is a limit governed by the zener as to how much your bike will charge the battery and it's reflected in your ammeter. If you have a discharged battery then your ammeter will show a strong positive charge, but as your battery's voltage rises, your ammeter reading will recede. The zener will dump any extra current so your ammeter will always show a small charge rate while you are riding along, until you idle for a while (maybe in traffic) which will draw on your battery's voltage. Then once you get moving again the ammeter will show a stronger charge rate momentarily as it replaces the lost surface charge, then go back to the normal charge rate so your components are balancing charge rate, the current draw of fixtures, and potential overcharging. (rotor/stator, electrical component demand, and zener control)

turn ignition switch to headlight, lo beam H4, while still running
at idle needle is at minus 6amps
2000rpm , needle at minus 3amps
3000rpm, needle at minus 1amp
4000rpm, needle is at zero amp

This sounds like your headlight circuit must be part of the problem. At 3000 rpm's you still aren't generating enough current for excess current to be charging your battery. At 4000 rpm's you're charging barely enough to keep your battery from draining. It almost sounds like you've lost magnetism in your rotor OR you have some other stator output issue, because at 4000 rpms the current flow direction should be positive, but it isn't. If not for your ammeter testing, showing normal current flow with the headlight off, I would think it was a rotor/stator chargine issue or a rectifier issue.

It seems like something related to the headlight circuitry... because your non headlight ammeter readings look normal to me...
 
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FWIW, I just did a similar test on my bike and with headlight on had to get to 4000 rpm before it showed charge current. I have a 3 phase 210 watt alternator and Li battery.
 
FWIW, I just did a similar test on my bike and with headlight on had to get to 4000 rpm before it showed charge current. I have a 3 phase 210 watt alternator and Li battery.

Thank you, What is your exact battery and exact voltage regulator?
 
Thank you, What is your exact battery and exact voltage regulator?

Shorai 21 AH battery and Sparx alternator/regulator. It puts out maybe 13.2V at 3000 rpm which is just barely adequate for a Lithium Iron battery.
 
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