T5 Alternator Light

T’other week on me commute, the T5’s alternator light, wouldn’t go out till I got to about 3500rpm, that was the only problem I had. Then last week, I stops for petrol, restarted the bike, and the light never went out, no matter how many RPM’s it did…

So, checked the Rotor, Stator, at me local electrical place, they said they were OK. Swapped out the Diode Board with a known good one, swapped the regulator over as well, checked all the Earth wires, cleaned all the connectors, even the buggers that ya can’t find…!

AND STILL, that bloody light stays on, and I’m not getting a charge at the battery with the engine running…

Tired and emotional I be, been up since 00.30 this morning, coming back from working in France, so perhaps as I’ve not had any real kip, MAYBE I’ve missed something…? But that gallon of paraffin, with the box of Swan Vesta, is looking mighty close…

Course this WOULD have to happen, just as me tour of Scotland is on the horizon, any electrical Ex-Spurts in Kent that can be trusted with a fine Moto Guzzi…? I’m at the end of me rope…

Just a thought. I have a T3 rather than a T5 so I am not sure if they are similar, but have you checked if the big connector block that on mine feeds into the right hand side of the headlamp shell is fully home? As you had stopped for petrol: if you had put it on the side stand the handlebars would naturally go to the left, which puts this connector under axial load.
May not apply of course but I thought I ought to suggest it.
Hope you get it fixed very soon. All the best,

Thanks, but that’s one of the connectors I went for, done em ALL now, it’s REALLY doing me bloody Ed in… A sweet running bike, but with no charge going into the battery, it’ll soon turn into a dead elephant…

You might have a broken wire ~ also check resistance of rotor across the brushes. Rotor winding should be 3.6 Ohms. Brush contacts may add a bit. If too much slip rings may need cleaning. Also check brushes have some life left and slide freely in their holders.

Don’t mention the brushes, they were the cause of the last no charge problem. Sounds like an SOS to Keith.Have you had a read of that Elektickery article. That has plenty of tests and checks to narrow down the problem. The fact that it does eventually charge and the light does go out suggests something is working but not fully to max potential.Did you have to change the rotor or stator recently?Have you done anything to the bike recently that might of damaged something?Putting a new battery on mine improved the charging, I think the old lawn mower battery didn’t like getting shaken about on the bike and there was a broken connection inside. Maybe swap a battery with Keith to rule that out as a problem

it did have a new rotor recently,will flash the rotor later when the bike is dropped offhave swopped out the rectifier & regulator for known good ones,electric gets to the stator just not out back to the battery,will go through everything again

Don lad, see I got the SOS out to Keith, and he’s coming to the rescue…

THAT, is what being in a club is all about, it still does me Ed in though, bloody electrics, sooner have a nice engine strip any day.

Suppose I’ll have to buy him a Haggis if we make it to where they live…

angus burgers

Check the earth on the negative side of the diode block.

woner full little club init,

That indeed is what it is Buzz lad…

As me brain was about to explode, Keith said he’d take over the search, seems to think it’s a broken wire somewhere…?

Silly isn’t it, worry more about me bikes than I do anything else, when they’re not well, I suffer, bloody sure I’m going mad as I get older. BUT, it IS a mighty fine motorcycle. And since I’ve had it, I’ve grown to love it. How weird is THAT…

Can’t wait to hear what it was, and as soon as the verdict comes in, I’ll let y’all know. Might be a while, I’m off to a BSA Rally in Belgium on me war machine, a week riding a girder forked side valve will put me right…

at the moment the ignition switch is looking suspectrechecked all connector blocks,belled out the charging systemswopped out rotor, stator, regulator,rectifier doesn’t leave much

Short circuit in the idiot light department?

dash is coming off in the morning to get to the switch,can check it all then,nothing else to check

BLIMEY… Who’d have thunk it, see I KNEW it’ll be something hidden, wonder if I can fit a nice Mag/Dyno to it, and get a kick start for it too. Don’t have any trouble like this with my other bikes…

Good on ya Keith lad, I can see you not having to buy ANY Ale at the V twin for this…

(Only just seen this) that's a very good point, I was shocked (shocked I tell you  ) how naff mine was when I rewired it last year. What made it naff is that apart from the rectifier uses the two lower mounting screws to connect it to the flimsy strips of metal it's mounted on, which is then in turn attached to the frame, but as an electrical connection this could be rust, SO they cleverly had the idea of adding a short bit of wire which goes to a bolt that holds a rubber side buffer for the battery to the frame, BUT this bolt can never be tight without crushing the rubber!     I replaced this with a longer piece of wire that takes the rectifier minus output direct to battery negative terminal instead. The fat negative lead goes direct to a gearbox rear cover bolt instead of frame (for starter motor).

So is 4 ohms across my slip rigs bad. I’m not charging at the moment so is 4 enough to cause it ?
Never mind , after 4 hours in the sun including cleaning up the fuse box I replaced the regulator. Bingo ! Would have thought that it would have lasted longer. Never even disconnected it until this afternoon.

theone&onlymin
xtheone&onlymin2014-07-04 17:03:43

Super!

If memory serves rotor resistance is 3.6 Ohms according to the book, anyway whatever it is to make 4 Amps at 14V. But as I’ve wrote before measuring very small resistances is notoriously difficult even with an accurate meter.

I remember a nice chap with a Guzzi and sidecar at Popham Megameet warning me about that earth when I was still rebuilding my T3 Cali. So when I did the wiring I made darned sure it was very good!!
All the best,

sorting it in the morning