1974 commando not charging

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roqueweiler

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Okay,

New plugs and battery and she starts right up, hot or cold or in between. Yay!

Cooler plugs (stock n7c champions) run beautifully => carbs are set up well.

Battery at 13.2 volts charged installed into bike.

Two or three 20 minute runs later (good long rides not stop and start)
battery is at 12.6 volts (no headlight)

Reading across terminals when running at ~3000 rpm is 12.3 volts

so, when running my voltage is dropping!!

The orange light on top left of the headlamp nacelle is going on at lower revs and off at higher.
I thought this meant it was charging when the voltage was higher than the draw. Is this right?

Am I correct in assuming I need a new voltage regulator?
Can someone tell me where it is on the bike so I don't pull the wrong thing?

Also where is the alternator? Do I have one? Is it shot?

I need a manual with pictures - any help here? I have 4 manuals; they might as well be written in greek.
Is there a repair manual for bozos anywhere?

Thanks again.
 
So, assuming you have a zener (usually attached to the Z-plates) it could be bad.

The more you can describe your electrical system (with pictures too!) the quicker folks can diagnose.

When you say "New plugs and battery" do you mean the battery is new too?

Possibilities are alternator, regulator (maybe a zener) or a short? Not necessarily in that order...
 
I would start by looking at your stator / rectifier. Some pictures would be nice. Stators in the Primary case and the rectifier is near the battery box( It is on my bike anyway) but my bike has seen alot of changes. Original rectifier looks like a stack (4) of thin plates with a bunch of wires going to them. I like to check the output of my stator with no battery connected to the system (Not possable for everyone though)
 
roqueweiler wrote;
Also where is the alternator? Do I have one? Is it shot?
Click to expand...
The alternator is found in the primary chaincase and is mounted on the end of the crankshaft. To expose it, you have to take the primary outer chaincase off, but this would probably not give you a lot of information except you would be able to see whether or not the lead coming from the alternator was intact, as it is possible for the wires to be become severed/broken where they enter the stator unit.

The first "obvious" place to look is behind the primary chaincase, behind the engine and in front of the gearbox, there will be a lead coming out of the back of the primary chaincase and there are usually two bullet connectors (sometimes 3 depending if it is high output) where the AC current connects to the main harness. This is where I would look first, and check that they are connected.

Beyond that, we need to know if it has the standard equipment on i.e. rectifier and zener, or if it has had an aftermarket "all in one" voltage regulator fitted. DaveK has described what the rectifier looks like, and the zener(s) are mounted to the Z plate(s) and will have a wire going to them. 1 on a pre MK3 on the right hand z plate and 2 on a MK3, one on each plate.
 
It's conceivable that your rectifier isn't bad but that the spade terminal has come off or the wiring is bad that's supplying 12V DC to the battery. Make sure the terminals are all secure on the rectifier under the seat. If so, test the negative feed to the battery to ensure that the alternator/rectifier/zener diode chain is supplying 12.8-14.6V DC to the battery when the engine is running and revved up. If not, your bike may be running entirely on battery power alone which will merely strand you two or three miles from home--recovering intermittently as the battery voltage rebounds between engagements.

Good luck


Tim Kraakevik
kraakevik@voyager.net
Three Commandos
 
I am indeed running on battery alone as it is "charging" at less than 12 volts measured between the terminals at 3000 rpm.

I am now searching for the culprit, although the manuals are infuriating as I have NO FRICKEN IDEA where anything is. Or what anything is for that matter - $%^&*&^%$%^Brits anyway.

I am now trying to check the nearly mythological "rectifier" which I understand in plain-speak to be the voltage regulator. I also understand that it looks like a stack of metal pancakes under my seat. I can follow the testing instructions I think!

The "Zener Diode" (whatever the F_iretr_UCK that is) is the next 'thing' to check. I have heard it is attached to another "thing" called a Z-ed plate.

Why are there no pics in any of my 4 manuals?


crap.
 
"rectifier" which I understand in plain-speak to be the voltage regulator

Rectifier recifies the AC output of the alternator to DC which suits a DC battery.

The Zener diode is the voltage regulator and makes sure your DC battery is not fried.

As far as I am aware none of these terms is solely British :mrgreen: .
 
A "rectifier" takes AC from the alternator and turns it into something your bike can use D.C.
It is easy to break by just tightening it too much or letting it get too loose for too long.
It can fail in a number of ways it works hard and needs care there are a number of meter tests that can be done to determine if it’s up to the job they are found in good shop manuals.
One test that is not done often enough and needs to be would be to check on the lowest A.C. setting on your meter as the motors running to see if it leaks A.C. If it is leaking into your D.C. system as little as 1 volt it will cause no end of problems.
The Zenor is a heat dump that clips excess volts and turns them into heat so mounting them to something that can take the heat and move it off to air makes sense. The two objects work together as a voltage regulator found on some bikes.
First get your thinking straight as to how it is supposed to work then get a good Lucas manual to do the correct tests to your components getting mad about it does no good. Do some long reads there is much to learn.
 
roqueweiler said:
Why are there no pics in any of my 4 manuals?
Click to expand...



The alternator is contained within the primary chaincase and is in two parts, a permanent magnet rotor on the crankshaft and a fixed stator.

Alternator
1974 commando not charging


The alternator supplies alternating current (AC) through two wires (white/green and green/yellow) to each outer terminal of the rectifier (which you should find near the battery?)
Rectifier
1974 commando not charging


The rectifier turns the AC current to direct current (DC) and supplies it to the electrical system through the brown/blue wire from the centre one of the three terminals of the rectifier (the single upper spade terminal on the rectifier is an earth connection)

The output from the rectifier is regulated (to stop the voltage rising above a safe level) by the Zener diode

Zener diode
1974 commando not charging


The Zener diode is on the inside of the right hand alloy footrest mounting plate or "Z-plate" (where the screwdriver is pointing) with its retaining nut on the outside, and should have a single wire connected to its large spade terminal with a red earth wire connected close-by?
Z-plate
1974 commando not charging
 
Two way a rectifier can go bad. 1. from hooking up the battery wrong. 2. from spinning the center bolt when mounting.
I have never known a zener to go bad directly but I am sure it has happened, probably from loose mounting.
I would validate the wires coming from the stator (and all other places) making sure their are no broken wires or loose connections. Check the stators physical condition. Check the wire coming from the stator's casing. Check to see if it looks burnt. Make sure you can slip .010 all aroung between the rotor and stator.
Lastly, if needed, get a new 180wattstator and remove any other doubt (the zener and rectifier)and get a Pedtronics Reg/Rec 200watt and ride all night long with the lights on high and the horn a blowin.
 
roqueweiler, I think youl find youl learn alot from the Britts if you take the time to understand the terms thay use.You may even get more answers to your qustions. Like someone here siad walk away for 10 minutes and youl have a new outlook when you return. Cant we all just get along?

Phil
 
thanks all

You guys are awesome.

Found all the "things" - will start testing as soon as I get my multimeter from home 1/2 hour away!

Also found a bunch more sketchy bullet connections and crimps which I have repaired - hopefully this is all it needed.

Pics posted helped IMMENSELY - I know that I have always hated auto electrical; British and German even more so.
I also know that one reason I hate it so much is my limited understanding of how it all works.

Little or nothing else to be learned from the Brits though having been surrounded by them my entire growing up period in Victoria BC <grin>
And I thought I knew all their stupid terms already - having to learn an entirely new set at my age is dodgy and makes me feel even more like a wanker.
 
Trumpeteer said:
roqueweiler said:
And I thought I knew all their stupid terms already
Click to expand...

"Stupid" terms. Don't forget there are Brits reading this that may be offended by that phrase!
Click to expand...

I can't think which stupid terms he could mean? :(

Rectifier? Can't be? I believe the first plate rectifiers were made by Westinghouse Corp. in the USA in 1933, and subsequently fitted to hundreds of thousands of motorcycles built all around the world, and I think the device has always been universally known in English as a "rectifier" ?

Zener diode? A British term, Surely not? Clarence Zener was American. :?
 
Oh sure, but what about the Victoria-Churchill-Hastings1069 unit? Can't blame us Yanks for that one! :twisted:
 
okay, verified that the alternator output at ~3000 rpm is about 17 volts AC (enough to zap me in a cut on my thumb - ouch)

but

the DC voltage at the battery is ONLY the battery voltage of between 12.4 - 13.3 depending on state of charge from my battery tender.

so,

I assume that it is Mr. Lucas' rectum-fryer that is the culprit, correct?

How much should I expect to pay for a new rectifier anyway?

And should I check any further before replacing said rectifying unit?
IE if I replace rectifier and the Zener is bad am I risking catastrophe?

thanks again

phil
 
roqueweiler said:
okay, verified that the alternator output at ~3000 rpm is about 17 volts AC (enough to zap me in a cut on my thumb - ouch)

but

the DC voltage at the battery is ONLY the battery voltage of between 12.4 - 13.3 depending on state of charge from my battery tender.

so,

I assume that it is Mr. Lucas' rectum-fryer that is the culprit, correct?

How much should I expect to pay for a new rectifier anyway?

And should I check any further before replacing said rectifying unit?
IE if I replace rectifier and the Zener is bad am I risking catastrophe?

thanks again

phil
Click to expand...

Podtronic
 
Hello Swooshdave,

Can I simply replace the rectifier with the podtronic unit without making any other changes or does it need teh 180watt stator?
 
17 Volts AC seems VERY low. I would almost say not acceptable. I remember an old post. I haven't checked my bike as It hasn't been a problem....I still say your stator.

General rule of thumb for every 24 Volts AC you put into the rectifier you get 12 Volts DC out.


QUOTE

"Hi David,yes the voltage is across the gn/y and gn/w leads from the alternator.This is AC volts.
Just checked my own bike and get similar,22v AC @ 2000 RPM and 32-35v AC at about 3000 RPM.
I haven't checked the make of replacement assimilator yet but it is a plastic/solid state copy of the old tin can with the same labelled connections.
From these readings I think the half wave rectifier should bring volts back to 11-16v DC and the Zener limit the volts to about 13.5v DC.
This seemed to be the case but after 3 dead ass's I wondered if anyone else had had a similar problem.
Stu's battery is fine although a bit low after a 100 mile run(with lights on),mine is the same,but I gues that's another issue.

Thanks for your help so far guys,Mike."
 
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