Charging A head scratching session???

[DrFarkoff]

A Gentleman gave me a call from the Thirty club today

He has an 83 R100CS in mint condition

His Problem starting from Cold the Bike runs perfect and charge rises to 13 to 14V approx depending on rpm

Now 3 miles later bike nicely warmed up and the charge just stops!

The red charge light comes on and the voltmeter descends to battery voltage

He came and borrowed a known good Regulator and then a known good diode board (in fact he borrowed 2 off me)

So overall there's no change it still does this.

I'm going to go see it on Sunday night to cast my eye over it I asked about the brushes
He reckons the brushes are about 5/8ths of an inch and the spring is not resting on the plastic brush holder Slip rings are clean

Connections under the tank and at the regulator are good and no verdigris??

Any other suggestions? I suspected maybe rotor windings separating when hot but surely then the charge light would not come back on???

Only 28,000 miles on this one

 

[ahutcheon]

Rotor windings shorting (insulation breakdown) when hot? Or stator coils doing something similar?

Just a couple of thoughts - I'm struggling to remember Guzzi electrics from more than a decade ago...

Edit: Or, having tracked down a circuit diagram, the stator coils going open circuit when hot. Those are the coil failure options that I can see that would stop generating but leave a path to turn the charge light on.

 

[Rob Farmer]

Sounds like a rotor failure to me. I had a similar fault on my 100/7 a couple of weeks ago. One of the wires from the windings had cracked on the shoulder of the commutator , just as it passes through the hole, as soon as the winding got hot the two pieces separated and it stopped charging.

Obviously it wasn't quite as clear cut as that to diagnose but a new rotor sorted it out.

 

[DrFarkoff]

Thanks folks ahutcheon I've never heard of a stator going open circuit before on one of these but it fits the bill no charge but charge lamp on

Rob I thought about rotor but if its gone you loose the charge indicating lamp don't you?

 

[ahutcheon]

I'm just suggesting possible faults which would match the reported symptoms, Rob F will have much more experience of what actually goes wrong in practice.

I figure if you're losing charge and getting the warning light without it being diodes, regulator or assorted contacts in the wiring (does the light come on full intensity?) then it could be either coils short or the stator open. Hey, if the diode board stopped feeding the voltage regulator when things warmed up but the warning light circuit stayed good you'd probably get the symptom you describe. But I've no idea if that's plausible with the actual wiring loom rather than just looking at schematics?

Good luck!

Andy

 

[Myke Rocks]

A f(r)iend had a problem with a rotor last year

Thanks folks ahutcheon I've never heard of a stator going open circuit before on one of these but it fits the bill no charge but charge lamp on

Rob I thought about rotor but if its gone you loose the charge indicating lamp don't you?

If the rotor goes short circuit, the fail to charge light will come on. If it goes open circuit, it will not come on.
As already suggested, rotor is probably going open circuit.
This fault drove a f(r)iend crazy last year, but I was able to check the rotor on his and prove that the rotor had gone open circuit on it.
Yours is more difficult, the diagnosis of an open circuit rotor is probably correct.
Myke

 

[DrFarkoff]

If the rotor goes short circuit, the fail to charge light will come on. If it goes open circuit, it will not come on.

Yours is more difficult, the diagnosis of an open circuit rotor is probably correct.
Myke

But the fail to charge light does come on so it can;t be open circuit can it?

P.S. this is the bit that was confusing me

I keep thinking back to Diagnostic basics Unfortunately I don't have the bike here to play with So I'd like to go armed with Information / bits

Problem = No Charge when warm + Charge lamp is illuminated

Changes made to date:-

• Connections cleaned and checked
• Regulator Replaced with Known good one (Original refitted)
• Diode board replaced with 2 known good ones (Original refitted)
• Brushes checked for length (serviceable)
• Under cover wiring checked for chaffing or trapped or corroded

Causes to date :-

• Short circuit rotor

• Open circuit Stator

 

[Rob Farmer]

Jay,

You've swapped everything except for the rotor. Give it a go.

We had the same issues when Bryn had a charge problem. He was sometimes getting no charge light when the engine wasn't running and the charge light sometimes came on while he was riding. Swapped the rotor out and all was good.

 

[DrFarkoff]

Yeah Rob it's the only moving bit so stands to reason really

I'll take my new one from Escargot up and try that

 

[DrFarkoff]

Okay to close this one up and add it to the collection of Tech "conundrums"

It was the rear brush

The outer tip of the Brush spring had been caught on the brush holder so the brush was not being pressed onto the slip ring full time and was arcing

The Slip ring was also running very slightly off centre exacerbating the brushes movement

The first pointer to it was the black carbon trace around two thirds of the slip ring

Anyway a tweak of the brush spring and making sure the brush was under tension at all times seems to have cured it