Commano electrical issue

Gents,
I have long been a lurker here but now I need to ask a question. Here is the situation. Completely renewed a 71 Cdo over the winter. New wiring harness built by me. For the first couple weeks the bike ran great with zero problems. Then a few nights ago the bike blows headlight and taillight and just dies. I get the bike home and discover that headlight and taillight bulbs are blown. Bike no longer getting spark.

I am running a Shorai battery, Boyer elec. ignition, Sparx 3-phase alternator, and Crane (CNW) single coil. Positive ground.

No melted wires. No frayed wires. Fuse did not blow.

I have the Boyer wired with white wire back from power switch, red wire and black wires to coil. Coil grounded to frame from same pole as the red wire. Yellow wires to stator plate. This is the way I wired it from day one and had no problems. If not connected to the coil the red wire is hot when I turn the key. But since I have the red wire connected to the ground side of the coil as soon as I connect the wire to coil I short to ground and the red wire goes dead. Again, this is the way I had it wired and the bike ran great. Now, with no changes, the bike blows the bulbs and loses spark.

What am I missing? I know the answer is staring me right in the face but I can't see it yet.

I think you need more ground connections. Along with the headlamp shell and taillight frame, here are other you should have.

If you have a positive ground system the red wire should not be "hot".
You have voltage coming out of the red wire?

Maybe the three-phase (Sparx?) reg/rec unit has failed and is shorting internally?

I am wondering if the voltage spiked rather than the current. The fuse is probably rated for a higher voltage than 12V, which would explain why it didn't blow. As for no spark now? I dunno, sadly it probably means that something else also fried. I would check the altenator literature about voltage regulation and then I would be looking at how to check the coil and the rest of the ignition components. This is just a hunch.

Russ

Guido said:

If you have a positive ground system the red wire should not be "hot".
You have voltage coming out of the red wire?

Click to expand...

Correct. That is why I mention it. It shouldn't be hot but is.

rvich said:

I am wondering if the voltage spiked rather than the current. The fuse is probably rated for a higher voltage than 12V, which would explain why it didn't blow. As for no spark now? I dunno, sadly it probably means that something else also fried. I would check the altenator literature about voltage regulation and then I would be looking at how to check the coil and the rest of the ignition components. This is just a hunch.

Russ

Click to expand...

That is what I am wondering. Did the VR fail and that is what prompted the failure through the system. The battery is fine and carrying a charge no problem. Would that be the case if the regulator failed?

HMBAtrail said:

Guido said:

If you have a positive ground system the red wire should not be "hot".
You have voltage coming out of the red wire?

Click to expand...

Correct. That is why I mention it. It shouldn't be hot but is.

Click to expand...

I suggest you try disconnecting the reg/rec red wire and see if that cures "hot ground wire" problem or not?

Excess voltage would be a likely cause of the bulbs blowing and also point to a problem with the reg/rec unit, excess volts could also damage the electronic ignition if it has risen above 16V.

L.A.B. said:

I suggest you try disconnecting the reg/rec red wire and see if that cures "hot ground wire" problem or not?

Excess voltage would be a likely cause of the bulbs blowing and also point to a problem with the reg/rec unit, excess volts could also damage the electronic ignition if it has risen above 16V.

Click to expand...

So you are suggesting disconnecting the voltage regulator power wire running back to the battery, correct?

HMBAtrail said:

L.A.B. said:

I suggest you try disconnecting the reg/rec red wire and see if that cures "hot ground wire" problem or not?

Excess voltage would be a likely cause of the bulbs blowing and also point to a problem with the reg/rec unit, excess volts could also damage the electronic ignition if it has risen above 16V.

Click to expand...

So you are suggesting disconnecting the voltage regulator power wire running back to the battery, correct?

Click to expand...

Yes, try disconnecting the either the red (positive) or black (negative) regulator wire (or both?), and see if that stops what appears to be battery voltage getting to the ground wiring.

Even with voltage regulator disconnected I am getting power to the red wire of the Boyer.

If the red wire is not hooked up to the coil then red wire is hot. If I hook the red wire and black wire to the coil (one to each pole on coil) then both poles of the coil go hot. If I add a ground strap from coil to the frame both red and black wires from the Boyer lose power. That makes sense if the red wire is hot and then I ground the hot wire that I get a short to ground. But no idea why or why it is happening now when it didn't before.

OK, so we can probably eliminate the regulator-at least for the time being.

However, it does seem as if there is a partial short somewhere back along that ground wire, the fact that you've done your own rewiring job does complicate things slightly as it is now something of an unknown quantity and I can only suggest you work back along the ground wire until you trace the cause of the problem?

Have you replaced the blown bulbs yet? If so, are they working normally?

What is the fuse Amp rating, and what type of fuse is it?

Replaced bulbs in head light and tail light and all is well there. 20 amp blade type fuse.

Agreed that since I built the wire loom it makes it more difficult to trouble shoot. But I did try and keep it as simple and straightforward as possible for that very reason.

I guess I will go through one at a time and try and see what I see.

Interestingly, the bulbs in the gauges did not blow. Only the headlight and tail light.

Kinda stumped.