Leaking Voltage at Battery Earth

[Trout]

Spend $25.00 & replace the switch, you can buy it here:
http://www.mgcycle.com/product_info.php ... 216fdfb9f5

Go back to basics. Follow Johns advice and check all the obvious things first. Pull the alternator cover: check for loose wires, worn brushes, weak brush springs, bad, corroded ground wires, etc. By the way: most charging systems charge through the switch and you have already established that as a "weak" link that's why I suggest replacing it.

"In the Old Days" (or who cares about this s**t anymore): Old timers would make their own load tester using any old starter motor and stepping on the drive while it was engaged. This caused a heavy "load" to be put on the battery and with the caps off the battery they would look to see if a cell bubbled, how hot the starter cable got and how many 1,000's it took to kill the battery. Load testing a battery is fine but you should also check it with a hydrometer. I've seen many that passed a load test but had a bad cell that will only show up using a hydrometer. A bad cell will keep a battery from holding a charge or fully charging, although they may still show 12v on a meter.

I have just come to a realization. These forums are a lot like sittin around the shop on old engine parts listening to everybody pontificate on their expert opinion. I miss the smell of old wood soaked in oil, cheap cigars & warm beer.

 

[Trout]

Supaflee,

Old Jock's post is accurate. You do have the Bosch system. The bulb must work for the charging system to operate. The highest rate failure item after the bulb is the rotor. Check that you have about 3 ohms or so from ring to ring. If an open circuit, the system won't charge and the bulb can't illuminate. Also disconnect the leads from the brushes and make sure there is continuity from the ground (D-) to the power connection (D+) from the voltage regulator at the stator. If the bulb does light when you turn the key on, you can jumper the two leads of the connection to the voltage regulator that are parallel (they should have the same color wires attached), but only run the bike briefly as you can over charge the battery. If the bulb goes out, the regulator is faulty, if not, stator id at fault, or possibly the rotor isn't producing an adequate magnetic field.

Thank you John!
This is what we used to call "full fielding" the alternator on car systems. I never knew how to do this on a Guzzi.

MORE Old Timer crap: A bad way to "test" an alternator was to pull the positive cable off while the car was running. The theory was if the car stayed running the alternator was working. Most of the time it would blow a diode and you ended up with a bad alternator anyway.

 

[Supaflee]

Thanks Guys. Seeing I know I replaced the charging bulb , which was burned black, Im sure its ok. But I will check it again. It hasnt illuminated at all since Ive owned the bike ( several months now )
Then I'm going to haul the cover off the front of the engine and do those checks you've suggested in there John.
( there may not even be a rotor in there for all I know at the moment ) :roll:
Im real grateful to have you Dudes on board here with my problem .
Ive found right throughout life , the biggest difficulty in problem solving is getting someone other than yourself to become at all interested in it ,,,,,,because it's not theirs, its mine .
So , tons of appreciation is aimed at you , thanks .
Supaflee

 

[john zibell]

Im real grateful to have you Dudes on board here with my problem .
Ive found right throughout life , the biggest difficulty in problem solving is getting someone other than yourself to become at all interested in it ,,,,,,because it's not theirs, its mine .
So , tons of appreciation is aimed at you , thanks .
Supaflee

That is why we are here. We are glad to help. Let is know how you make out.

Right now I'm more familiar with the Bosch system than I want to be. I just finished a months long project ( 31 hours billed, but it took a few more than that) of getting a guys 1970 R75/5 that had sat for 25 years back to a serviceable condition. After going through all the mechanicals, seals and gaskets and then getting her running I encountered cascading failures in the charging system. Repair one component, then another would fail. Three of the 4 charging system components failed in succession. Finally have her buttoned up and ready to go home.

 

[scottmastrocinque]

...I just finished a months long project ( 31 hours billed...

For you, CHA CHING!

For him, Arrrrrgh

 

[OldJock]

Hi Supaflee

If the bulb is not illuminating at all, there is a chance that your problem is right there. Do all the other stuff but I'd start to trouble shoot the generator light for sure. It should come on when you switch on the ignition and go out after starting. It may glow dimly at idle especially if the idle on the bike is low, but go out above 1500 rpm.

If it doesn't the usual fuse checks followed by checking the bulb (Oh and do not be tempted to use an LED, the charge system will not work properly).

If the wiring is standard the battery side wire at the bulb will be red I think, the side going to the rectifier is blue. I don't think Carl's diagram for Generator warning for the SP is correct as it shows the bulb grounded on one side and it shouldn't be. Take off the blue wire and place a temporary wire to the engine or frame on one side. Ignition On and touch your temporary wire to the bulb connection where that the blue wire normally sits on. It should light. If it does not then you will need to take a supply from one of the other bulbs to the side the blue wire is NOT on.

If it does light then the fault lies downstream. First thing after that is continuity of the blue wire going from the bulb back to D+ on the rectifier.

See how that goes then take it from there.

It's because the system uses an electro (as opposed to permanent) magnet on the generator rotor it needs a wee smidgen of electricity to wake it up and get it going. The bulb has 2 functions to tell you if the generator is not making electricity and also to boot the generator, wake it up and get it started. Once its started the whole system is self sustaining.

Hope that helps some more. No need to thank us, maybe I'll need your help someday.....who knows?

John

 

[john zibell]

Also note the ground source for the bulb when the bike isn't charging is actually through the voltage regulator and through the rotor contacts. Once the bike is charging, you have 12 volts on each side of the bulb and the light goes out.

 

[Supaflee]

Ok John , so you are telling me to provide a test circuit to the generator warning lamp, then continuity of the circuit existing on the bike to the lamp , correct?
Ive gotta go to the boat and get my bag of tricky stuff now , seeing Im about to set up some alternative supply etc .
Once Ive done these few tests ill come back to you .
I see there is an 80 Ohm resistor in the wire between the rectifier and the fuse block which feeds the red side of the lamp, what if it's kaput?
How do I identify the resistor on the bike , from your experience whereabouts will I be most likely to locate it , in the L/H sidecover for example or up under the tank ?
Supaflee

 

[OldJock]

Hi Supaflee

I guess if you refer to me by OJ or something then we can sort out which John is which or maybe John N (me) and John Z (the VERY knowledgeable Mr Zibell)

Anyways back to the topic in hand.

That resistor is there as a back up to allow the generator to get kick started (or flashed to use the terminology) if the charge bulb failed by providing an alternate feed. If it is there then that may not be your problem and we can move on.

The resistor is in most of the diagrams with bikes that have the Bosch generator. All I can tell you is that I totally rewired my LM V and never found it. You could check for it by going to the the relevant fuse (fuse 3 on Carl's diagram) removing the blue wire from the back of the box and test resistance to D+ at the rectifier. On my rectifier there was only the one wire on that lug which came from the lamp.

If the bulb was working and the resistor was also there the pair would provide approximately double the current to the alternator rotor than the bulb alone making the rotor coil very magnety indeed.

If the bulb was working and the resistor Kaput then the system would still work

If both were Kaput then the chances are the system will not work (although sometimes it just might due to residual magnetism, but its very iffy)

Its your choice of course but I would still like to have a charge warn light if I could and Yes I'm asking you to check part of the bulb circuit. I am asking you to check if you have a +12 feed to the bulb. John laid out the second bit in his last post too.

The charge warn bulb is fed +12 from the battery and its probably a red wire. When you turn on the ignition the circuit goes: battery, bulb, D+ rectifier, regulator, brush, rotor coil, brush, ground. So its got a path to ground and the bulb lights (rotor resistance is low so it has negligible effect).

When the system is working there is voltage at D+ so you have a positive voltage on both sides of the bulb. As the volts are the same no current can flow and the bulb goes out.

John Zibell has also given you some tests. So you can attack the fault from various directions, John Zs are more generic on the system and I'm concentrating on the charge light which may or may not be the problem.

I don't know if you have a multimeter but if you have it will certainly help on the diagnosis. They are relatively inexpensive and a very handy tool to have.

Good Luck

John

 

[rbm]

The resistor is in most of the diagrams with bikes that have the Bosch generator. All I can tell you is that I totally rewired my LM V and never found it.

It is possible that the resistor is made up of a resistive wire. I'm not saying it is, just that it might be. I know that the heated hand grips on BMW K-bikes have two stages of heat - Hi and Low - which is achieved by switching in a resistor into the circuit to get Low. The resistor is a resistive wire and not a separate component. Since the alternator on the LM V is a Bosch manufactured device, Bosch may use the same technology. You could have understandably overlooked the wire especially if you were looking for a component while rewiring.

 

[OldJock]

Valid enough point Robert.

I never did check the line with a meter as I was thinking it would be a component.

The resistor would only have current passing through it for a short time normally and dissipate approx 2W if there was a problem. That's not much of a load so it is feasible to do it that way too.

If Supaflee checks the resistance of the line from the blue wire on the fused side of #3 to D+ then that should still tell him definitively if there is a resistance, wire length or component. It will return somewhere in the region of 80-85 Ohms if its there and probably less than 5 Ohms if its not.

John

 

[Supaflee]

I got my bag of stuff from the boat . Now to do some tests for continuity and resistance and stuff.
This is so cool having you knowlegable Dudes on board with my problem .
Please dont go too far away , it may be a day or so before I can get a good go at the darned problem. My Bike's in the garage( car shed ) and its terribly cold and miserable in there .
Supaflee

 

[Morizzi]

The resistor is in most of the diagrams with bikes that have the Bosch generator. All I can tell you is that I totally rewired my LM V and never found it.

It is possible that the resistor is made up of a resistive wire. I'm not saying it is, just that it might be.

That's actually a really good point but it is very unlikely to be the case here. We are talking 70-80s Italian electrics, not anything high tech. :lol:

No resistor, no resistor wire, if the bulb blows the battery goes flat. Its how it has always happened to me but rarely fortunately. I've never worried about it. In most of the models I've had/have there is a brake fluid warning lamp. Its like carrying a spare globe. At worse shove some tin foil in there. I always check my idiot lights on start up.

I've purchased Tontis in 3 continents, had various models and never found any difference in the charging circuit of any of the bosch bikes.

Just my experience.

Rod

 

[Trout]

Thank you Old Jock & John Z for your very concise instructions. Charging systems have always been a weakness of mine & this helps a great deal.

 

[Supaflee]

OJ . The web page which is highlighted in red in your earlier post is a danger zone for my computer. Somehow I think its been hacked or something .DONT GO THERE. It caused my computer to lock up completely.
On a better note , I've found a 83ohm resistor in the wire between the Rectifier and the Fuses.It was all bundled up like spaghetti behind the fuses. inaccessable .
I've yet to prove that I've got 12volts to one side of the ignition lamp with the ignition switched ON.
I'll report on this later tomorrow .
Thanks Dudes

 

[OldJock]

Supaflee

I am sorry if any of these links caused your computer to lock up, Major Apologies!

I just revisited both of the links and neither caused a problem for me. One does throw up some sort of warning, but its a red herring. The site is hosted under "This Old Tractor" by Gregg Bender and is a very useful site for things Guzzi. That actual article is still a bit of a work in (very slow) progress though

The BMW Airheads link is a very good explanation of the system. BMW and Guzzis of that era used identical systems

I suppose if there is any doubt though better to steer clear..... weird

If anybody wants a copy of either of these articles if they PM me with an email address I'll send them via email to eliminate the possibility of hacked or dodgy web pages.

Back to the problem

I assume that the brushes were in good nick and all the connections are good. Bad brushes are a major cause of problems too.

If you have the resistor and it works maybe its getting voltage to the field at ignition on and its not the problem. You could check by measuring the voltage on the DF connection (on the generator) with the meter to DC and the other side to frame. When you switch on you should see a change in Voltage but it will be small, between 0.25 and 0.5 of a Volt (most of the Volts are dropped across the resistor and/or bulb).

I'd still try to work through it step by step and positively eliminate stuff as you go.

If its getting a "flashing" voltage to the field winding (aka rotor) the next thing is to test the generator, but rather than confuse the issue lets go a step at a time.

Did you try any of John Zibell's checks yet? Just curious, I will feel stupid if you ignore his advice and he has nailed it first post

Trout

Thanks for the compliment, Mr Zibell is the real deal, but I'll help if I can and if I know what I am talking about. Honestly they are not so difficult once you get your head around them. Glad to be of assistance

John

 

[Supaflee]

OJ, voltage at the ignition lamp with the ignition on =zero , checked for continuity of bulb=good. checked one feed wire =zero, checked other feed wire= zero.
Now Im going right away back to the huge multi pin plug under the tank to see whats going there.
I'll report again later .
Oh , yep , I tried all of the stuff that John Zibell suggested, it sort of concurrs with what you've said at times , so if Ive thanked the wrong Dude ,,,,,,,,,,,, well I guess neither of you will mind .
Im going to check the brushes now as well .
Corrrrrrrrr, this is driving me nuts .
Regards Supaflee

 

[john zibell]

OJ, voltage at the ignition lamp with the ignition on =zero , checked for continuity of bulb=good. checked one feed wire =zero, checked other feed wire= zero.
Now Im going right away back to the huge multi pin plug under the tank to see whats going there.
I'll report again later .
Oh , yep , I tried all of the stuff that John Zibell suggested, it sort of concurrs with what you've said at times , so if Ive thanked the wrong Dude ,,,,,,,,,,,, well I guess neither of you will mind .
Im going to check the brushes now as well .
Corrrrrrrrr, this is driving me nuts .
Regards Supaflee

Until you get voltage at the bulb, the charging system can't work. Start tracing back until you find the open circuit. See https://www.guzzitech.com/forum/160/3001.html

 

[OldJock]

You are hunting down things one at a time.

Any supply will do to get a voltage to the "Charge Warn" bulb. You could double up on the supply going to the "Oil Pressure Warn" for instance and use that, assuming you have it.

With the brushes; check they are not worn, are not sticky in their holder, can lift in the holder, spring back easily onto the slip rings and make good contact with the slip rings (the copper ring they sit on, on the rotor). Check the slip rings are clean.

You could lash up a temporary supply with a wire from the battery to the "Charge Warn" to see if it lights at ignition On and goes out when you start the engine, then check battery Volts to see if the system is actually charging. Before taking Voltmeter readings at the battery, ensure the battery is good and has been charged up (with a charger). If you take Voltage readings with a partially charged battery, the battery can influence the readings.

Although you obviously have a problem with the bulb being wired wrong or the supply faulty, it is possible the system is still getting "flashed" at start up via the resistor you mentioned earlier, but its not a certainty.

Keep at it your getting there

John

 

[Supaflee]

Thanks OJ. you are an inspiration to young Dudes like me ( 61).lol :lol: .
This will make you spew , late yesterday I realised that the LOW BRAKE FLUID lamp stays on from when the ignition is switched on , it never goes off .
My bike has had the integrated braking separated and doesnt have a low level fluid switch in any reservoir to switch the lamp on.
I wonder if the wire connected to it has been put on the wrong panel lamp, and the generator warning feed is connected to the Low Brake Fluid Warning Lamp by mistake ??
I believe the generator lamp has no feed , because the feed is on the wrong lamp . I'll prove that today .
I checked the brushes at the generator slip rings . They are free to spring in and out and are clean , as are the slip rings themselves.
I'll do exactly as you suggest ,and run a separate feed from the battery to the generator warning lamp . That'll prove your theory about the feed to it being messed up somewhere , and it'll confirm my realisation and thoughts regarding the Low Fluid Warning Lamp being continuously illuminated also ,,,,,,,,wont it ? AAAAAAahhhhh, now there's more ,,the Low Oil Warning Lamp doesnt go either , even when I bridge the switch at the crankcase , something funny there tooo. :?
As you say , one thing at a time , gradually I'll knock 'em over .
Thanks Supaflee.