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LeMans III Charging System Problems

J

Jon O

Just got it firing!
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Battery won't stay charged, in fact just turning the key starts draining it rapidly. I replaced the charging system idiot light bulb and I can't get the new bulb to light up. I even made sure the new bulb was good by plugging it into the neutral light wires and get it to light up there. But when I plug it into the charging system idiot light wires, it won't light up.

Any ideas for me before I start blundering around looking for problems in my 28 year-old, Italian wiring harness? Thanks in advance for any advice.
 
Ah Jon, the "joys" of the Bosch charging system, common to your LM III & my T3FB. I am by no means an electrical whizz, but have had to mess with my charging system (or more commonly, have it messed with for me) many times over the 33 years I've had the T3. First, do you have a copy of Guzziology, which will give you lots & lots of good advice on this? If not, shame on you, get one forthwith from MI. Beyond that, some thoughts. Oh, & I assume you don't want to just bring it in to Mark or Sean & just let 'em do it for you, right Jon?

1)Are you really, really sure your battery is not toast? Not uncommon for batteries to "test" good, but still not really be good. Best would be to swap out with a known good battery if possible. If your battery is several years old, might be a good idea to replace anyway. I'm still using $50 Interstate SP30R open cell lead acid batteries in my T3 with great results, lasting 3-5 years.

2)I know for a fact that in the T3 & some other models (unknown if this applies to LM III), if the charging bulb is bad the charging system will not charge. No joke. If as you seem to be saying a known good bulb does not come on even with ignition on & bike not even started, most likely culprit is the bulb socket. Mine has these fragile wires to make contact-but all I had to do once was scrape off a bit of corrosion. Can't say for sure if that could be causing a charging issue, but why not?

3) With the motor on (recharge battery if you have to) & headlight on also (optional on my bike, probably not on yours)-does revving the motor over, say 4-5k make the headlight obviously brighter? If the battery is weak but the charging system at least sorta working, headlight should get obviously brighter. Or use a multimeter measuring across the battery. At 4-5 k you should get, oh, 13.5 volts or better I would think. If it never goes above what it shows with the motor off, then obviously it is not charging.

4)Charging light bulb & battery issues aside, by far the most common fault in the Bosch charging system is the alternator rotor. I've replaced/rewound several over the years. You measure resistance between the two copper slip rings at the front of the rotor. Should get about 3 1/2 ohms per Guzzilology. Bad ones usually show infinite ohms. My memory is that you have to isolate the brushes from the slip rings before taking this measurement, with the motor off of course.

5)Other things like the diode rectifier & voltage regulator can go bad, but on the Bosch system rotor much more common. See Guzziology or someone more knowledgable than me for further advise.

Hope this is of some help.
 
guzzibob said:
2)I know for a fact that in the T3 & some other models (unknown if this applies to LM III), if the charging bulb is bad the charging system will not charge. No joke. If as you seem to be saying a known good bulb does not come on even with ignition on & bike not even started, most likely culprit is the bulb socket. Mine has these fragile wires to make contact-but all I had to do once was scrape off a bit of corrosion. Can't say for sure if that could be causing a charging issue, but why not?
Click to expand...

Alternators make power by having their rotor induce a rotating (electro)magnetic field to their stator.
But their rotor has no permanent magnets, like ps on the japanese bikes generators with the rotating flywheel/magnet - the rotor unpowered, is just a dead coil.
So if you just rotate the rotor, no power comes out of the stator.

For power to be generated by the alternator you must have the rotor powered firstly by the battery.
So when you turn on the igition a current passes from the battery to the rotor through the bulb.
If the bulb is not on (burnt or poor contacts through the rotor brushes or wore out rotor) then no current passes through the rotor so no power comes out the alternator however fast you rotate it.
When the stator starts making power upon the powered rotor being rotated, the bulb goes out as the stator feeds the 1-2 amps needed by the rotor stopping the current that comes from the battery through a diode and lights up the battery bulb.

So for the bulb to light up you must have a battery and an alternator that is not producing any power because it has stopped rotating. Of course the rotor must make good contact with its brushes and the bulb must not be burned out or make poor contact...


(Why put an alternator and not a generator? Much less inertia, I suppose, in particular when you already have a heavy flywheel.
And why have a generator instead of an alternator? I think this gets you a steadier load through the regulator-load whatever the actual loads are (lights-turn signals etc) when idling which makes small or multi cylinder not torquey engines much easier to tune for proper running at low rpms).
 
Battery is new and known to be good. Shows 12.92 when charged up. When I turn the key to on but don't start the bike, it drops to 12.10. Is this significant? Shouldn't it only drop a little bit when you turn the ignition on? When I start the bike and bring the revs up it stays at 12.10 or drops to 12.00.

Charging light bulb is new and known to be good. Socket is good too, I tested the bulb and socket by plugging the neutral light wires into it and getting it to light up that way.

The neutral light and the oil light are working, so power is making it through to the next idiot lights in the circuit.

A friend looked up a wiring diagram and came up with:

The red wire comes from the fuse box and then jumps from the charging light to the the oil and neutral lights. The lights on either side of the charging light are working so everything must be OK here so far.

The other wire ( Blue ) goes to terminal 61 on the rectifier. it appears that inside the rectifier, it also jumps over to the D+ terminal then externally from the rectifer , goes to D+ on the voltage regulator. So does this mean I should test the rectifier and voltage regulator next? If so, how?

This is all I know for sure so far. I'm pretty mentally challenged when it comes to testing electrical stuff but I can learn if someone spells out exactly what I need to do next. Thanks!
 
I have just been thru this with my 850t(74 ), same symtoms which was traced to an open circut rotor. This rotor looked fried when I got the bike and I was surprized tha it worked at all ( lasted a week after recomissioning ). I have fitted a rectifyer off a lucas acr alt and a 2 wire bosch regulator. I actually rewired the whole bike as it was a basket case when I got it , and it sure is different to my 900ss and paso :D
 
The Bosch system is a good if somewhat underpowered setup - as the rotor runs at crank speed if you are just idling it may barely charge. As you are probably aware, the same system is used on the BMWs of the same vintage (caution: the BMW rotor looks the same but is slightly smaller in diameter producing weaker output - to be sure have your original rewound or check upon receipt

1. Buy a $10 multimeter. Analog is fine if not preferable as it is less likely to jump around as some cheap digitals do.

2. Set it to measure resistance on the lowest setting and measure the resistance across the rotor slip rings with connections to the slip rings removed. There should be continuity. If not your rotor is fried - this is the no. 1 problem. Tip1: Guzzi makes a spacer that allows air to circulate through the housing and prolongs the life. Tip 2: do not sand the rotor slip rings as some old hands suggest: the carbon actually improves conductivity.

3. If the rotor is ok, measure the resistance on the stator just to check. Again gross continuity is what you are looking for. The stator almost never goes wrong and if it does it is likely to be only one coil producing a pulsing headlight (same for the rectifier).

4. Set the meter to volts, turn on the bike's lecky and check for 12VDC at the feed to the rotor. It should be about the same as the battery - if not check connections, charging lamp, ignition switch and the regulator. Tip 3: you can put a resistor across the charging lamp circuit so that it will function even if the bulb is duff.

If it has the old mechanical type regulator replace with an electronic one such as they do here: http://www.euromotoelectrics.com/ or here http://www.motoelekt.com/. You can also find one from some 70's american car if you can deal with parts counter people. The adjustable one is good move if you intend on using a glass mat/deep discharge battery.

5. If the rotor is getting power and the system is still not charging, check continuity from the output of the battery back to the battery. The rectifier can be checked by setting the multimeter to resistance and checking for continuity - it functions like a one-way valve: you should have continuity one way and not the other for all 3 phases. Again replacement rectifiers are available fairly cheaply (the motoelekt one claims to be an improved version) from the mobs mentioned above or can be fixed at your local ye olde auto electric shop - if they haven't yet disappeared. You can also solder in appropriate diodes yourself if you are handy. Tip 4: don't be tempted by the simplicity of the single rectifier/regulator black box - they are non-repairable and IMO more likely to fail as they are potted which according to MIL 217 reduces the MTBF by about 20%. With the OEM setup you can still get home if the regulator fails by wiring the rotor directly to the battery (which is also one way of testing the circuit - just remember to remove power when you turn off the bike or you will fry the rotor - at above 3000 RPM you should be seeing 14.4 or so volts at the battery).

Unless you need the power, the bosch system is simple, easy and inexpensive to sort and pretty bullet proof.

Im boco lupo,

Chris R
 
Bulletproof? The Bosch charging system? Not remotely. They eat rotors, although how long they last can vary wildly. Several on my T3 over the years. Plus I have seen several on the road at various rallies with the same malady. When the Bosch was the norm, there was always someone advertising rewinds in the MGNOC newsletter, or talking about where they get them rewound, for way less than the $250 or so Guzzi wanted for a new one. Plus the aformentioned ridiculous need to have the neutral light working in order to charge, plus the occaisional (though much less common than rotor failure, fortunately) diode failure. Even the immediate successor to the Bosch, namely the Saprisa on my 1000S is far more reliable courtesy it's permanent magnet rotor, even though no higher output. Easily fixable, perhaps, bulletproof, not in my experience. I eventually mounted a voltmeter on my T3 in case the rotor would die on me out in the middle of nowhere so I would know to shut off the headlight immediately, & therefore get much further before I had to recharge or start walking. To me, the main weakness on the roundhead & early squarehead Tontis.
 
Bulletproof? The Bosch charging system? Not remotely. They eat rotors, although how long they last can vary wildly.
Click to expand...

Like all things italian, sorting things out is the price of admission. If you are a pureblood consumer (and I doubt you are) who thinks you can buy something and out of the box it will perform perfectly forever, buy a Honda and pray a lot. That being said I had a honda and it ate regulators.

I would say that the statement that Guzzi's 'eat rotors' is pretty hyperbolic. I have had one rotor failure in about 240K of guzzi riding and for most of my riding buddies it is about the same. It might be different if I rode in the high desert.

The rotor is a pretty simple thing - just wire. If it fails it is because the wire used had a flaw in it - which happens with anything mass produced, it wasn't properly potted or there was no insulators on the wires before the slip rings or it overheated. I have rewound a few rotors - it is actually very easy. You need to make a ring that fits over the rotor so the tangs don't splay and a big hydraulic press. Other than that, it is just wire wrapped around a spool. Teflon tube on the wires as they pass through the rotor is good.

As I mentioned before guzzi does a spacer that helps with the heat. Removing the crossover tube on lemans etc that cooked the rotor and made access difficult also helps.

For the light you can either carry a spare or put a resistor across so if the light does fail the system still works. All alternator systems of that vintage worked that way. Also Motoelekts fancy regulator does not need the charge light for 90$.

The Saprisa is less fixable - if the black box goes on the road you are done. With the Bosch, if the regulator fails, any junk yard will have diodes you can fit, same goes for the regulator.
 
My SP rotor failed at 55K miles. Mark at MG Classics says they seldom make it past 50K.. not what I'd call bullet proof. The system is simple to troubleshoot, though..
 
I am not familiar with Guzzi fitted alternators but I must say that a rotor's current increases when the alternator's output is not adequate for the loads as the regulator tries to keep up the power output.

In general, the alternator's output is dropping along with rpms so the rotor's current increases if you ride all the time on low rpms increasing thermal loads and rotor contacts wear due to the higher current through the rotor coil and brushes.

On permanent magnet generators on the other hand, there is always a high output that gets consumed at the regulator as rpms increase - the regulator acts as a compensating load and not a feedback element, as far as I know that is...

So maybe the difference in your riding styles maybe to blame for the life difference you have experienced.
 
Mi_ka said:
In general, the alternator's output is dropping along with rpms so the rotor's current increases if you ride all the time on low rpms increasing thermal loads and rotor contacts wear due to the higher current through the rotor coil and brushes.

So maybe the difference in your riding styles maybe to blame for the life difference you have experienced.
Click to expand...

Suggesting my T3 eats more rotors cause I ride at lower RPM's than the average bear? Not a chance. If anything, since I replaced the stock VHB30's with 32 PHFs which means that there is actually some benefit to spinning the thing, this T3 may run at higher RPM's than many others. By no means abused, though. Actually if you have a spare rotor with you & the few minor tools needed to pop off the old one, after allowing the bike to cool off enough to not get burnt you can swap them out in 15 minutes or so. Or alternately, if you have a voltmeter so you know to shut off the headlight immediatly after it dies, I found I could generally get 200 miles on a fully charged battery on my Dyna ignition T3, then stop for the night & a recharge at the nearest service station, then do it again if need be. Still, I'll take the Saprisa on my 1000S over the Bosch on my T3 anyday. It's just provided a lot less hassle over the years, with or without the spacer on the T3 alt cover.
 
The rotor is a pretty simple thing - just wire. If it fails it is because the wire used had a flaw in it - which happens with anything mass produced, it wasn't properly potted or there was no insulators on the wires before the slip rings or it overheated. I have rewound a few rotors - it is actually very easy. You need to make a ring that fits over the rotor so the tangs don't splay and a big hydraulic press. Other than that, it is just wire wrapped around a spool. Teflon tube on the wires as they pass through the rotor is good.
Click to expand...

Chris

Could you provide any more info? Any pictures of the rotor apart? I'd like to try a rotor rewind but not to shure of the way the tangs are pressed on (or off) and how to salvage the rings without busting them?

Tom
 
tewrecks said:
The rotor is a pretty simple thing - just wire. If it fails it is because the wire used had a flaw in it - which happens with anything mass produced, it wasn't properly potted or there was no insulators on the wires before the slip rings or it overheated. I have rewound a few rotors - it is actually very easy. You need to make a ring that fits over the rotor so the tangs don't splay and a big hydraulic press. Other than that, it is just wire wrapped around a spool. Teflon tube on the wires as they pass through the rotor is good.
Click to expand...

Chris

Could you provide any more info? Any pictures of the rotor apart? I'd like to try a rotor rewind but not to shure of the way the tangs are pressed on (or off) and how to salvage the rings without busting them?

Tom
Click to expand...

Or get a re manufactured one for $90.00 http://www.motoelekt.com/charging.htm Be sure to call Rick and tell him it is for a Guzzi and not a BMW (slight difference in fit on the crankshaft). His are machine wound so more turns in the cage than you can get by hand wrapping.
 
I don't need a rotor, I'm just trying to learn about rewinding one.
 
Could you provide any more info? Any pictures of the rotor apart? I'd like to try a rotor rewind but not to shure of the way the tangs are pressed on (or off) and how to salvage the rings without busting them?
Click to expand...

It is so long ago that I burnt up a rotor that I don't actually remember if I pressed it apart from the centre or via the tangs! I do suspect the tangs as I remember making a ring to keep the tangs from splaying. There is no need to wreck the commutator rings. In which case you need to get two pieces of pipe and cut out some teeth so they touch the end of the tangs.

The rotor is just two pieces that fit together with a taper - nothing special.

Sorry no Photos.

Once apart you need a paper or plastic bobbin to wind the wire on - they used to be standard at ye olde auto electric but not so much anymore - I think I just found something dimensionally correct. We have a winder at work but you can do a good job by hand.

That then has to be potted in varnish - again ye olde auto electric will have the right stuff. i used some super duper polyurethane conformal coating from work.

Teflon tube on the leads as they go through the rotor is a good idea.

Again I haven't had a bad experience with the bosch as others have. This may be luck or my skill in rewinding rotors. I do agree that you certainly can't ride it in such a manner that you abuse the rotor.

Or get a re manufactured one for $90.00 http://www.motoelekt.com/charging.htm Be sure to call Rick and tell him it is for a Guzzi and not a BMW (slight difference in fit on the crankshaft). His are machine wound so more turns in the cage than you can get by hand wrapping.
Click to expand...

I noticed that euro do a rotor, rectifier and solid state rectifier for 140$ - which is a real bargain if it is a proper guzzi rotor as john points out. I have nothing against the Saprisa - just the price and I would carry a spare black box.
 
Thanks Chris. I got as far as getting the copper rings off only to find that the tangs section was spot welded, so that concludes my effort on this one rotor for now.

Tom
 
Hi Tom

I don't know what is spot welded - maybe you can send a picture? Maybe they have changed the design but when I did mine it was standard automotive practice.

And I now remember what I did. I took some suitably sized pipe and cut castellations that touch the end of the tangs using a band saw so I had a bottom and top holder. I also (after bending the tangs on the first one I did -oops!) made a ring on the lathe that loosely fitted over the rotor. It takes a surprizing amount of force to break them apart. It is just a taper so I don't know why that is so.

There is no reason to touch the commutators to take the rotor apart. If they are in ok condition you can epoxy them back into position - if not then see if Ye Olde Electric shop has a spare or get out the lathe.
 
Thanks Chris. At this point this learning experience requires more effort than anticipated, so until I get motivated again, other priorities need attention. But thanks again.
 
OK, here's an update to my LeMans III charging system problems. I replaced the idiot light bulb and it still would not light. I put in a new alternator rotor and now the idiot light bulb lights up. But now it stays lit no matter what. Hooked up a voltmeter while revving the bike and it's not charging. So next I put a new voltage regulator in. Same result. I've tried different loaner stators, different loaner rectifiers, still won't charge. So all four components of the system (rotor, stator, rectifier, voltage regulator) have been replaced at this point and still it won't charge. I've checked for continuity on the new rotor and it tests good. The old one definitely tested bad as well I've tested for continuity at the alternator brush terminals and they check out good too. So all I know for sure right now is that the original rotor was bad.

Guzziology mentions polarizing the alternator by touching a wire from the positive battery to the positive post on the alternator for just a second as something else to try when the problem defies logic. Am I at that point yet? Any ideas for me?
 
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