850T-3 Not Charging

[Piston Broke]

New diode board is installed and still not charging. I noticed that one side of the three-prong spade connector had potting epoxy dried on it. I filed off enough to fit the plug but maybe I need to pull the board back off and clean that spade better. The bottom looked clean so I thought it would make a good connection. Otherwise it's time to find one bad wire throughout the bike, a daunting task for me to say the least. I'm open to any specific advise on what exactly to check and how to check it. I've had plenty of people say "you've got a bad ground" without any information as how to find a bad ground within the 1/2 mile of wires. Thanks a ton for everyone's help thus far, Cheers!

[Tkelly]

Probably not your issue but is it possible that you lnstalled the new board incorrectly?Dont ask how I know.

[guzzisteve]

 I guess you can't read service manual, it TELLS you how to test each part. It is all there in black & white for the reading.

[Piston Broke]

I guess you can't read service manual, it TELLS you how to test each part. It is all there in black & white for the reading.

Ouch! My Haynes manual does not go into detail, just says "check". But I read zero volts at the alternator with the bike running. Again it says to take to a specialist for inspection. My service manual does not go into details that I could find either. Sorry, I'm lost and just need some help to diagnose the issue instead of just throwing more parts on it that I may or may not need. Thanks for any other advice.

[n3303j]

Looked at your profile, no location.
Wondering where you are located.
Must be someone in your neighborhood who could pop over and lend a hand.
Lots of wires, but decent documentation. So time and a meter will provide an answer.

[n3303j]

Beyond Haynes Manual, from Greg Bender's website.

https://www.thisoldtractor.com/mg_manuals/workshop_manual_g5_lemans2_sp_t3.pdf

[guzzisteve]

factory manual

[Moparnut72]

The Haynes manual I have is awful. It assumes too much and doesn't go into detail. I have a replacement diode board and regulator, I haven't gotten far enough along to run the motor so I can't report. I have done my own wiring and left a lot of the factory stuff out. The project is on the back burner at the moment, riding weather and yardwork etc is taking more of my time.
kk

[Piston Broke]

I'm in Grand Rapids, MI. I do have a friend to help but he is currently out of town.

[Dukedesmo]

Assuming your rotor/brushes are good, have you checked the voltage at the brushes? Asking because, as per my post a few up, mine was not charging and when I measured the voltage at the brushes, there was nothing.


The cable to the alternator on mine has 5 wires in it; 3 (phases) to the alternator output, a +12v to one brush and a feed to the centre winding of the stator with the second brush taking it's feed of 12v- from the ground through the casing (apparently some bikes have 6 wires, of which the extra is a 12v-/ground to the second brush).


The connection to ground on mine was 'dodgy' and adding a wire direct from battery to the brush appears to have fixed it, either way it can't hurt.




Above pic shows the alternator; red clip is on one brush, white to centre feed of stator, the second brush (inbetween) has a tab for a cable but no wire connected, it simply takes it's power through the body of the stator and that is where I added the new, direct from battery -ve to. 


 

[blackcat]

Duke, minor issue but the brushes should be at 12 o'clock for gravity purposes.

[John A]

Duke, minor issue but the brushes should be at 12 o'clock for gravity purposes.

There was a service bulletin to put them on the side because in the vertical plane they would bounce and loose contact on rough roads.

[n3303j]

Duke, minor issue but the brushes should be at 12 o'clock for gravity purposes.

"Gravity Purposes" ??? First time I've ever heard that one! What are they, about 3 grams each. More disruption from bumps rather than gravity being misaligned.

But the spring pressure is supposed to exert about 250 - 350 gramd downward on the brush to guarantee intimate contact. The spring will install in two orientations 180° opposed from each other. One installation puts about 1/4 turn tension against the brush. This is wrong and will allow the brush to bounce and arc,  ultimately burning the contact rings. The other mounting location puts about 3/4 turn preload on the spring and about 250 - 350 grams thrust load on the brush. This is correct and the slip rings will last forever.

[Dukedesmo]

OK, interesting but AFAIK they've been like that for nearly half a century, sure I've removed the alternator a couple of times but refitted it as it was.


Seems to work OK so I'm minded to leave it as is.   

[Moparnut72]

I have a partially disassembled T3 which I just checked, the brushes are at 12 O'Clock.
kk

[n3303j]

My 1966 850 T3. This orientation worked well with the stock length harness connections.

[Frenchfrog]

12 o'clock was the standard original position but it was superseded because it tended to aggravate brush bouncing.
I moved mine to the recommended position decades ago even though it seemed to work fine...zero issues in either case !

[blackcat]

OK, I stand corrected.