Electrical Blues

[drerock]

Hello,

I have a 79 XS1100

When the bike is on, and the revs are high (over 5000) only about 12 volts is getting put across the battery. The battery is new.

After testing the voltage reg/rec, using the guides posted on this forum, I determined that some of the resistances were off spec so I replaced the reg/rec. This did not fix the problem.

I work at a small bike shop, and the owner and long time bike guru told me to check the AC voltage across the white stator wires. These were giving 80-100 AC volts, which was apparently good.

We then checked the resistance between each of the white [stator] wires and ground (as checked at the disconnect which goes directly to the alternator). It was about 0.4-0.5 ohms.

He says that those wires should go directly to ground, and the current could be simply grounding out instead of "pushing" through the reg/rec.

I have checked thoroughly through all of the connections and wires for breaks and melted harnesses etc. but all looks good.

I've posted with this problem before, but hopefully this new information will help.

Thanks in advance

-Eric

Note: The red wire coming out of the reg/rec was modified on the previous unit to have a wire directly from the battery spliced into it, before it went into the wiring harness. I don't know why, or what this means.

[DiverRay]

Eric,
Two items to check!
1. follow the wires from under the ignition switch, and check to make sure none of them are "burnt" from over-heating. There should be a brown wire from the switch, going through the harness, to the reg. rec. Verify that none of the connectors from the alt to the harness, the large white connector BEHIND the fuse block, are "burnt". You should have seen these as you check for the voltage from the alt.
2. Take the ignition switch off the bike, and pull the back apart to check the wires. If you have a problem there, you won't be "turning on" the reg/rec, and no charging.
I've replaced the wires on the back of mine with new, marine grade wires. It seemed to help.

[randy]

We then checked the resistance between each of the white [stator] wires and ground (as checked at the disconnect which goes directly to the alternator). It was about 0.4-0.5 ohms.

Eric, Those white wires shouldn't have ANY connection to ground. An ohms check between any white wire and ground (frame) should read infinite resistance.

An ohms check between any two white wires should show the .4 - .5 ohms resistance.

[drerock]

Maybe I misunderstood, and he meant exactly what you said.

The resistance between white wires does appear to be ~.6 ohms.

I'm all out of ideas

[skids]

I have seen a few charging failures because of the clip behind the fuse block. It is worth cleaning it. The volt-regulator depends on grounding to the frame where it is mounted. This is another place to clean for good contact. The rotor is not worth messing with. It simply spins with the crank and oscillates the magnetic field back and forth so that the stator (also a non-moving stationary device) can generate current. Check the magnetic field against the alternator cover with the key on and using an iron object like a cheap screwdriver tip. The magnetic field should be good and strong and is produced by the field coil. I haven't heard anything about a field coil test from you yet... If you have no magnetic field or it is weak, the volt regulator is not sending it any current (or it is not making it there), BUT you did say that you measured a lot of AC volts coming from the alternator, so I am wondering if it was measured at the VR or if it was measured on the alternator-side of the connector that lives behind that fuse panel... I keep coming back to that connecting clip, I don't know why!

[drerock]

I did test the alternator for a magnetic field, and it appeared to be fine. On my bike, the 'Fuse Block' doesn't really exist, whoever redid the wiring just sorta connected them all in that area.

The AC voltage was measured at both the VR and at the 'Fuse Block' connection, with similar results. When changing the VR, special care was taken to ensure good contact with the frame.

When I tested the field coil, I got ~10-20% more resistance than the spec. Which seemed reasonable.

Thanks for the input.

[Miti-Babe]

Eric

As as Skids said:

The volt-regulator depends on grounding to the frame where it is mounted. This is another place to clean for good contact.

It's ESSENTIAL that the rec/reg unit has a good earth connection... The lower of it's two mounting bolts should have two ring terminals mounted under it... These are frame "earth" connections for the wiring harness and one of them is directly connected to the black earth wire on the rec/reg unit...

The reg/rec unit produces an output (red wire) which is relative to the voltage sense input (brown wire) If the connections between the battery and the brown wire to the rec/reg are questionable, this relative output will be too...

That's why Ray queried the connections on the ignition switch, etc...

The (basic) route for the voltage sense input is as follows:

Battery +ve to Main Fuse (Red HD, double insulated cable)
Main fuse to Ignition switch (red HD cable)
Ignition switch to fuse box (brown HD cable)
Fuse box distributed through harness (brown cables)

As your PO made some wiring "modifications" Check to make sure that the brown (signals) circuit is separately fused from the red (charge) circuit... The rec/reg depends on this separation to develop the voltage difference between input and output... If they're connected directly together, the charge circuit may never work correctly...

Good Luck

Miti