Le Mans 2 battery charge / light glitch-update.

[Stevex]

My Le Mans 2 has its original wiring loom and the startus interuptus mod incorporated.
Yesterday after about 5 minutes riding, over a period of about a minute, the battery charging light came on and the headlight indicating light went off, about 3-4 times, lasting a second or two. My wife confirmed over our intercom that she could see the headlight going off and back on in her mirror. Apart from that, the journey was without problems.
I've had the ignition switch apart previously to check its internals which appeared fine.
Normally, even though the battery should stop charging, the lights should stay on, if selected, should they not?
Any ideas how these instances could be linked, I can't see anything obvious looking at the wiring diagram?

[guzzisteve]

Lights will go out or dim if battery is dead or charge is insufficient to the point it's not 12V, look at charge issue. Alt or diode board, rotor, brushes, ETC

[Stevex]

The charge light came on for no more than a second or 2 at a time and the battery is fully charged.
Even though the battery wasnt charging for that small time it would still be fully charged so the lights should stay on.
No different to putting the ignition on and switching the lights on without starting the engine.
I cant see the common denominator that links the two.

[pehayes]

LeMans 2 was not sold in the US.  Instead, it was modified and re-badged as CX-100.  Do you have a real LM2 or the US alternate.
Handlebar switchgear is horrible design.  Prone to many contact issues.  Lots of electrical functions going through these switches.  I fought the same switches on my 87 SPII.
Maybe someone has a replacement option.  Not likely to be plug and play.  You'd have to splice into the wire loom.

Patrick Hayes
Fremont CA

[Antietam Classic Cycle]

LeMans 2 was not sold in the US.  Instead, it was modified and re-badged as CX-100.  Do you have a real LM2 or the US alternate.
Handlebar switchgear is horrible design.  Prone to many contact issues.  Lots of electrical functions going through these switches.  I fought the same switches on my 87 SPII.
Maybe someone has a replacement option.  Not likely to be plug and play.  You'd have to splice into the wire loom.

Patrick Hayes
Fremont CA

Stevex is in the UK, so it's a LM2 for sure. Here is a photo from one of his recent posts:



 

Likely not a switch issue IMO.

[Stevex]

Yep, original UK Le Mans 2.
I've got the oem switch gear and it's never been a problem in my 10+ years ownership.
What I should have done was look across to my voltmeter and twiddled the ignition switch, oh well.
I see there is a replacement ignition switch but it takes spade connectors not bullets. I seem to remember the last time I went inside the original switch it looked good although there was slight wear on some of the dimples on the saddles. I don't suppose anyone has been inside a replacement switch? I'm wondering if it has saddles I could transplant. It would save using 2 keys for the bike.

[blackcat]

My CX did something similar to your bike, then it lost all power. Fortunately I was almost home and just had to push it up a hill to get it in the garage....anyway, it was the original ignition switch. Like most of the original wiring on that bike it was in bad shape so I just replaced the switch with a Zadi switch.  In your case I'd remove the switch, which isn't easy and clean up the wires and the switch, then spray it down with Detoxit.

[huub]

you've got a issue with the grounding of the headlight/ instruments.
worst case just add another grounding cable from the frame to the headlight bracket

[moto]

Here, for those who might not have it handy, is the wiring diagram for the Le Mans 2:

http://www.thisoldtractor.com/guzzi007/schematics/1978_LeMans_II.gif

Since the ignition switch does not separately serve the headlight, the problem won't be in it. I think Huub's suggestion of a bad ground at the headlamp housing sounds good. A new ground wire is easy to add and would be my choice for a simple diagnostic and possible cure.

[Stevex]

Thanks for all the inputs, some good pointers there.

[Kiwi_Roy]

Here is the LeMans II schematic

http://www.thisoldtractor.com/guzzi007/schematics/1978_LeMans_II.gif
A typical hard to understand Guzzi comic.
I think there might be an error in the drawing of the dash printed circuit (13), I believe item Oil Pressure Light (18) Charge light (19) should have power on the left hand side, the drawing doesn't show that.
The red wire 6 up from the bottom of item (13) is powered from fuse 3 powered from the ignition switch via a fat Brown wire.
If you trace the red wire from the Charge light (19) you will see it ends up at the rectifier terminal 61 then it goes through the rectifier board and ends up at the regulator D+.
The small forward current through the charge lamp is enough to provide initial Voltage to the alternator rotor but this is only required until the 3 vertical orientated diodes in the regulator take over.
then the charge light goes out.
 
I suspect the headlight is losing power  at Fuse 3 and the charge light is back feeding (in reverse of normal) from the rectifier which is now at 12+ Volts because its spinning. Note: the headlight and charge light share fuse 3 It would be easy to check this, with the motor running and headlight On remove fuse 3 and see if it duplicates what you observed.
Check all the fuse connections if it has those awful european fuses held between a couple of spring clips I would pull the fuses and polish up the ends by rubbing on rough cloth (I rub them on my jeans) and make sure there is lots of tension on the springs, some owners stretch an O ring around the clips to provide extra tension.
I'm also suspicious of the wiring around the ignition switch it looks as though the kill switch (27) must be fed from the switch (8) terminal 50 via the white wire, maybe the switch contacts aren't shown correctly and terminal 50 is alive with key On

[Stevex]

Roy, thanks for your input, I'll take good look at the fuses and give them a clean.

[Kiwi_Roy]

http://www.thisoldtractor.com/guzzi007/schematics/1978_LeMans_II.gif
Luiji didn't fuse the ignition coils on this bike, you may want to add a fuse between the battery and ignition switch, maybe a 40 Amp in-line blade fuse at the battery terminal.
In the red wire between battery Positive and the rectifier + terminal, beter to blow a large fuse than letting the magic smoke out of the wires.

[acogoff]

   And Check your Grounds. Bad Grounds lead to very wonky behavior.

[Kiwi_Roy]

I wonder where Stevex is at with this problem?
My money is on lack of tension on the fuse holders.

[Stevex]

I checked the fuse holders, they are solid and well tensioned. Been away for a few days but intend to take the Guzzi out and see what happens, checking ignition switch and dash voltmeter indications.

[Stevex]

Finally managed to get the Guzzi out for a ride to see if I could reproduce the fault and look closer at the indications.
Over a 45 miles ride I had to wait until mile 32 before anything happened.
I noticed as before, the headlight went out and the charge light came on. Wife behind me saw my back lights go out at the same time, so not just a headlight prob.
Also looked at the voltmeter and it was reading zero.
I turned the lights out at the switch gear and the charge light went out and the voltmeter indicated charging. Over a period of a mile or 2 I turned the lights back on, they came on, and then the above repeated itself a couple of times. After that the bike did the final 10 miles or so without problems.
On one occasion, with the lights on, I noticed the voltmeter needle slowly going down and when it reached the low red zone the light indication went out and the charge light came on. I recycled the headlight switch and it went back to normal but the needle on the voltmeter went up slowly, rather than indicating full charge immediately.
So, looking back on my original post and observations, I've also noted that all lights go out, not just the headlight (indicators still worked) and the charge light comes on with the voltmeter falling to zero.
As soon as the lights are turned off the charge light goes out and the voltmeter indicates charging, but the needle can take a few seconds to indicate a full charge.
Does this change anyone's opinion as the what the fault may be and a possible cure?
Thanks in advance for any advice.

[guzzisteve]

Lights will go out or dim if battery is dead or charge is insufficient to the point it's not 12V, look at charge issue. Alt or diode board, rotor, brushes, ETC

Battery won't take charge anymore, bad battery, bad alt or rotor, bad diode board.
CHARGE LITE is ON, volt meter is 0, it runs on battery till it's dead from no charge. Check charge system---it's not working after 30mi, could be rotor wire coming loose w/hot, same w/alt windings, diode board

[Frenchfrog]

Or the rotor going bad...never had a dodgy one personally but back in the day they did tend to get cooked and then die.

[guzzisteve]

I would check your Ohms when your charge lite is on not off or use a heat gun. Nothing wrong w/wiring. Slip cardboard from matchbook under brushes.
There is also a shortcut for the regulator, to check it on a Guzzi or BMv. Any Tonti manual will give you the Ohms not just your model.

[Stevex]

Although Im not sure why, being a mechanical engineer rather than an electrical one, Im seeing a correlation between the initial fault and the fact it immediately resets i.e. charging resumes, once the lights are turned off.
I'll whip the alternator cover off and have a look.

[guzzisteve]

I'm not an engineer, I'm a mechanic more than a technician, You said charge light stays on after lights shut off. I don't overthink it. Takes less than an hr to test all charging components.
My bad, just reread it, goes out w/lites are off

I happen to have a service manual for your bike in hard copy I bought in early 80's. Says you may have a printed circuit board on dash or un- printed. Big clear wiring diagram (2 pages big)

I'm thinking bad voltage regulator, not keeping up with the load on system.

[Stevex]

Yes, I've got the dash printed circuit board, same as the CX100 and Spada. I have the coloured wiring diagram on my PC.
I took the alternator cover off and checked everything I could, all looks good.
In my limited experience on electrics, usually a faulty component just dies, not throwing up an intermittent fault.
If the diode board blew a diode it would be a permanent fault, like wise a voltage regulator. The electrical load on my bike is low, both headlight and rear lights are LED.
Recycling the lights resets the fault and charging re starts. Is there anything in the charging system components that would allow this to happen?

[guzzisteve]

 A faulty voltage reg will, they don't just go bad, some get slow before. I have seen alt rotors that loose it when hot.
The wires on the positive side of diode board is a place to look. It's where the wire goes to battery, volt reg, fuse board, it's B+, D+ & 12V
It may be crowded by there w/wiring, see if all looks good, no corrosion.

If I'm thinking correctly volt reg increases as load is put on, it should go enough to charge battery too. If not it's bad.

I got to go work on the Jeep ignition, be back later. Rain stopped.

[Stevex]

I've just replicated the exact symptoms while running the bike on the centre stand.
Before starting the bike I noticed slight movement of the ignition key with ignition on, made the 3 dash lights flicker.
Sure enough, with the engine running, lights on and putting slight movements on the ignition key, the lights went out and the charge light came on.
New post coming up for possible switch repair.

[guzzisteve]

Good catch, sorted out.

[John Croucher]

https://www.ebay.com/itm/364868715360

I installed this in a 850T.

Red, hot from ignition key
3 yellows to stator
Black ground
green negative on stator
2 oranges positive on stator. 


Guzzi cheap.

[Kiwi_Roy]

I've just replicated the exact symptoms while running the bike on the centre stand.
Before starting the bike I noticed slight movement of the ignition key with ignition on, made the 3 dash lights flicker.
Sure enough, with the engine running, lights on and putting slight movements on the ignition key, the lights went out and the charge light came on.
New post coming up for possible switch repair.

Thats great feedback, although I blamed a loose fuse holder the bad switch had the same effect, another one to put in the memory bank.

[Tom]

Open up the ignition switch again.  Scrape the flat contact point.  You might have a build up of plastic/crud on that part.  Take the part out.  Place on a piece of glass to see if it's flat.  If not, tap lightly on the spring side to flatten.  Light tapping w/screw driver.

[Kiwi_Roy]

Sometimes the grease in the switch is to blame, it can get quite stiff over time holding the contacts apart.
This happened to my first Guzzi one of the green VII Sports, I measured 18 Ohms between the contacts.
I advocate cleaning out the old grease and replacing with fresh, soft Vaseline.