79 XS750 Stator

Garc

New Member
Sonreir said:
Without having the black wire from the R/R connected to anything?
No sir, if black is disconnected no voltage in either white/green loose with plug red +12V/green ground and verified <.1 resistance. Battery is 12.5~13.0 static.
 

Garc

New Member
That loose green has direct continuity to chassis ground, that can’t be right from your diagram.

In fact I just checked every terminal on the entire R/R and they all have some sort of continuity through each other.
 

Sonreir

Oregon
I've gotten a bit lost and I'm having a hard time picturing what's going on. OK if we reboot?

When you hook up the R/R according to the diagram, things are not working, correct?

If so, leave everything connected, turn on the key, and check for voltage on both wires going to the field coil (either green and brown and green and black, depending on your year). Please report back with the DC voltage readings you're getting.
 

crazypj

Split personality, I fake being smart
Have you tested wiring harness for continuity? Yamaha were notorious for having bundles of wires crimped together inside harness, one could easily have broken after 35~40 yrs. The XS wasn't as bad as the smaller bikes, they often needed replacement harnesses before they could be sold (un-crate, put a battery on it, do a warranty claim ::) ) The worst were the intermittent faults, may work for months then just stop. Spent many hours fault finding on Yamaha's (Suzuki's were easy, almost always blown R/R, and stator after owner fitted a new battery without testing anything)
 

Garc

New Member
crazypj said:
Have you tested wiring harness for continuity? Yamaha were notorious for having bundles of wires crimped together inside harness, one could easily have broken after 35~40 yrs. The XS wasn't as bad as the smaller bikes, they often needed replacement harnesses before they could be sold (un-crate, put a battery on it, do a warranty claim ::) ) The worst were the intermittent faults, may work for months then just stop. Spent many hours fault finding on Yamaha's (Suzuki's were easy, almost always blown R/R, and stator after owner fitted a new battery without testing anything)
I have probably tested them all through troubleshooting, but for the sake of getting the electromag/field coil functioning I'm eliminating the harness by going direct from battery/ground into the R/R and through the stator/coil without any success.

I'm one step away from replacing the stator that actually static tests 100% fine, I just need more clarification on if the R/R is operating and routed correctly to satisfy the EM system.
 

Sonreir

Oregon
For the R/R, the main thing to verify is that you're getting voltage on the white wire. Is that tests out OK with how you have it hooked up, then the other tests are handled with the bike running.
 

Garc

New Member
So we have battery voltage on the white wire through the R/R following your wiring diagram.

Pulling the power from black signal removes 12V from white.

Going to brown on the field coil with the white wire and green/green creates a spark that blows my signal 12VDC fuse.

Between green and brown on the 3 plug field coil we had 3.6 ohms both ways. We already proved those were the 2 windings.

Is the alternator bad or the Rectifier/Regulator?
 

Sonreir

Oregon
Garc said:
So we have battery voltage on the white wire through the R/R following your wiring diagram.

Pulling the power from black signal removes 12V from white.

Going to brown on the field coil with the white wire and green/green creates a spark that blows my signal 12VDC fuse.

Between green and brown on the 3 plug field coil we had 3.6 ohms both ways. We already proved those were the 2 windings.

Is the alternator bad or the Rectifier/Regulator?
A bit too early to call it just yet, but something isn't adding up. How many amps is the fuse rated at? Any resistance between the brown field coil wire and ground?
 

Garc

New Member
Put a 20 amp fuse in, 12.5 battery voltage and 12.2VDC through signal wire and white wire hooked to brown field coil.

Loose Green wire R/R connected to green field coil now shows .06VDC.
 

Garc

New Member
No continuity from any of the 3 from the coil plug to ground but I'll verify this evening as things are beginning to blur together.
 

crazypj

Split personality, I fake being smart
There shouldn't be continuity between Brown and ground, until you have the other end of coil plugged into harness
 

Sonreir

Oregon
crazypj said:
There shouldn't be continuity between Brown and ground, until you have the other end of coil plugged into harness
Exactly. But if there is low resistance between the field coil brown wire and ground, then this would be the cause of the fuse popping.
 

Garc

New Member
Charged the battery up to 13 volts, key on shows .125VDC between green through the coil and chassis ground.

The green/brown field coil field wire to ground is showing 1.2-1.4MOhms
 

Sonreir

Oregon
Hmmm... still missing a piece of the puzzle somewhere.... I'm trying to think of what might be next...

Brown wire (from the field coil) that's connected to the white wire (from the R/R) has 12V on it?
 

Garc

New Member
White R/R wire to Brown Field coil typically has .2VDC under direct battery voltage when through the meter to battery or chassis ground.
 

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