KZ400 fuse destroyer

I started with the tests. I measured voltage between the positive terminal of the battery and the output of the main fuse. There was no reading. But then I turned the key and surprise: 11,30v.

I mean, I'm at this point:

 

I have observed that if I operate any other switch the reading goes up to 12.5V

Any suggestions? I'm going to check the handlebar controls.

well, a good reading with your probes in that postion especially with the switch on would be 0.0v.
When you get a voltage of 11.3v that means you have an issue on that circuit.

Did you blow the fuse?

While you have the 11.3v reading..
Do not disconnect any connectors.
Leave the key on.
Keep your red  probe on the positive battery terminal( metal part of the battery)
With your black probe, measure on that wire towards the red probe. When you get 0.0v you will have found your problem.

Make sure to measure the fuse and the fuse clips.
 

I think we are talking about different tests. The test I've done is without a fuse, and the voltage reading indicates that the output of the fuse is grounded somewhere in the circuit.

But disconnecting the regulator the voltage disappears. The wiring is fine. The motorcycle does not blow the fuse when cold with the ignition on.

It is the typical bastard failure that appears only when the bike warms up.

So I only have two options:
- check the output voltage to see if it is getting too high and that blows the fuse (I'm going to look at it now)
- Short that appears when hot or when some part of the wiring is moved with normal use of the motorcycle. Probably headlight area or other moving areas.

Feanor_twh wrote:

I think we are talking about different tests. The test I've done is without a fuse, and the voltage reading indicates that the output of the fuse is grounded somewhere in the circuit. Agreed

But disconnecting the regulator the voltage disappears. The wiring is fine. The motorcycle does not blow the fuse when cold with the ignition on. If your RR is electronic is it the OE or aftermarket combined unit which normally has 5 wires (none of which are connected to the Ignition circuit )- How have you wired it ????

It is the typical bastard failure that appears only when the bike warms up. It may not be temperature related, a partial short will take a little time to overload the fuse

So I only have two options:
- check the output voltage to see if it is getting too high and that blows the fuse (I'm going to look at it now)
- Short that appears when hot or when some part of the wiring is moved with normal use of the motorcycle. Probably headlight area or other moving areas.

Voltage doesn't blow fuses, current does. If I have time later I will put you a "test plan" together

Wookie58 wrote:

Feanor_twh wrote:

I think we are talking about different tests. The test I've done is without a fuse, and the voltage reading indicates that the output of the fuse is grounded somewhere in the circuit. Agreed

But disconnecting the regulator the voltage disappears. The wiring is fine. The motorcycle does not blow the fuse when cold with the ignition on. If your RR is electronic is it the OE or aftermarket combined unit which normally has 5 wires (none of which are connected to the Ignition circuit )- How have you wired it ????

It is the typical bastard failure that appears only when the bike warms up. It may not be temperature related, a partial short will take a little time to overload the fuse

So I only have two options:
- check the output voltage to see if it is getting too high and that blows the fuse (I'm going to look at it now)
- Short that appears when hot or when some part of the wiring is moved with normal use of the motorcycle. Probably headlight area or other moving areas.

Voltage doesn't blow fuses, current does. If I have time later I will put you a "test plan" together

www.oregonmotorcycleparts.com/V_regsEM.html . I have the VR3-KZ regulator that connects exactly the same as the original. I have measured the output voltage with the engine running and it remains completely stable at 14.5V, in any RPM range.

The short circuit does not appear at cold, I wiggled the wiring but the voltage did not appear. I have to shake it even more.

I find it interesting that a partial short will take a while to overload the fuse, I hadn't thought of it that way. But it seems difficult to find the point of short in those circumstances.

The fact that the voltage does not blow the fuses, the current does, I thought so. It's a matter of amperage, the fuses support 250v or even more.

Feanor_twh wrote:

I started with the tests. I measured voltage between the positive terminal of the battery and the output of the main fuse. There was no reading. But then I turned the key and surprise: 11,30v.

I mean, I'm at this point:

 

I have observed that if I operate any other switch the reading goes up to 12.5V

Any suggestions? I'm going to check the handlebar controls.

Feanor it's good to see that you are using my guide, however you need to read the section fully and digest. Also don't skip any steps or you will disappear down a "rabbit hole" and drive yourself mad. The section you are using specifically says "disconnect consumer" - (this is because your voltmeter will see a path to ground through un-switched consumers when there is no voltage supply to them)
 

You need to concentrate on the section that applies the principle to a circuit with multiple consumers

 

Below I have given a suggested way forward - intermittent faults are always the hardest to find 

   

Wookie58 wrote:

Feanor it's good to see that you are using my guide, however you need to read the section fully and digest. Also don't skip any steps or you will disappear down a "rabbit hole" and drive yourself mad. The section you are using specifically says "disconnect consumer" - (this is because your voltmeter will see a path to ground through un-switched consumers when there is no voltage supply to them)

You need to concentrate on the section that applies the principle to a circuit with multiple consumers

 

 

I take note, I will investigate from there too. I think that this note is useful enough to be in the guide.

.

Below I have given a suggested way forward - intermittent faults are always the hardest to find 

 

 
 

I checked the resistance of the field coil and it is within normal values (cold).
I think I could take it apart (which doesn't seem complicated) and stress it with a hair dryer, then measure the resistance.
Would it be a valid test?

The resistance of the field coil isn't the issue, I suspect when everything is hot (the field coil and the engine casing) that the insulation is breaking down. This won't potentially effect the coil resistance but it will allow it to "bleed" to ground. The test I have suggested is probably the easiest and most accurate

Wookie58 wrote:

Below I have given a suggested way forward - intermittent faults are always the hardest to find 

 

 

I took the motorcycle out onto the street (everything connected) and after going about 30 meters the fuse blew. I checked the voltage across the coil, zero. I put in a new fuse and drove for a while (with everything connected), it didn't fail again.

I will repeat the test, and at the time of failure I will repeat the exact steps you have indicated.

When I did this fix (automotive fuse holder), as soon as I started the fuse blews (30 seconds).

But since then none have blown again, and I have done nothing more than replace the blown fuse with a new one. Maybe was a bad fuse? They are all recovered from scrapping.

So I couldn't do the test you told me. I will continue using the bike, and will write again when there is any news.

Thank you all.