1978 Kawasaki KZ400 Fuse Short (?) and Blinker Issues Question

Yes, remove the tank and follow F64’s careful diagnostic procedure.

Just a note I forgot to include.
When taking the meter readings the red/blue wire, brown wire fuse must be removed.
You want that circuit isolated.

Okay so I finally got some time and disconnected both the brown/white + red/blue fuses and the blue/white + blue fuses and tested them. No issues on red/blue (0.01v- 0.07v), but on solid blue I get 12v. But from the wiring diagram I think that's running to the headlight, which I haven't removed, but it persisted even after I disconnected the terminals so I'm not sure that that means. 

Also-- any idea what this random brown terminal might go to? It isn't the extra brown white and I can't find it on the diagram.
 

AdAstra029 wrote:

Okay so I finally got some time and disconnected both the brown/white + red/blue fuses and the blue/white + blue fuses and tested them. No issues on red/blue (0.01v- 0.07v), but on solid blue I get 12v. But from the wiring diagram I think that's running to the headlight, which I haven't removed, but it persisted even after I disconnected the terminals so I'm not sure that that means. The blue wire will see ground through the headlight bulb - if with the headlight bulb disconnected the blue still gives a 12v reading then there is a short somewhere between the fuse, the headlight dip switch and the headlight itself

Also-- any idea what this random brown terminal might go to? It isn't the extra brown white and I can't find it on the diagram. If you look on the diagram below and left from the brake light failure unit there is a brown wire with a double connector that doesn't go anywhere
 

Also, new question-- why wouldn't the tail light be running? From what I've seen, that just runs straight from the ignition switch to the light to ground. The brake light works, so surely it's not the bulb (unless that's just how dual filaments work) and it's not the ground because the stop lamp is still fine. I double checked and the wire is connected and running all the way to where it needs to be. Should I check that connection on the ignition switch itself? 

Have you checked if there is ignition voltage at the connector on the red wire for the tail light by the lamp unit ?
The two filaments in a dual filament bulb can and usually do fail independently of each other (the tail light filament works harder so is most likely to fail)

NEVERMIND 

Whatever blew the tail light the first time apparently isn't an issue anymore-- I reinstalled the fuse that blew the first time and flicked it on and the stop light WORKED so now we're just trying to figure out the blinkers.

Would the possible short we found on the blue fuse affect that issue at all?

AdAstra029 wrote:

NEVERMIND 

Whatever blew the tail light the first time apparently isn't an issue anymore-- I reinstalled the fuse that blew the first time and flicked it on and the stop light WORKED so now we're just trying to figure out the blinkers.

Would the possible short we found on the blue fuse affect that issue at all? No - the blue wire only feeds the headlight dip switch. The blinkers are fed from the brown wire which is the main ignition live powered by the 20 amp main fuse. Does it matter which side blinker you operate that causes the fuse to blow ?

That main fuse doesn't blow when I use the blinkers. I have no idea what caused it to blow the first time, actually. For now I ran some voltage readings on the brown wire and the tachometer light and found that both are only receiving about 10-11 volts max. 

Could undervolting be the cause of the issue? The battery's fine-- i just charged it recently and it's been giving me 12v everywhere else I've tested it. From what i understand that means I might have a terminal or a ground I have to inspect. 

That voltage is low on the brown line. What is the battery voltage?
With everything connected put your red meter lead on battery + black meter lead connected to the brown wire (with it still connected) now switch on the ignition. Any more than approx 0.5v indicates a "resistance" fault. Follow the resistance fault section of the "elec diagnosis" guide (link in my signature) to find the point where the voltage drops (could be multiple smaller drops along the way due to corroded connectors etc)
It is unlikely that this alone is the blinker issue as the flasher unit works on current not voltage.

Battery voltage is currently 11.9v
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I read an 0.6v drop at the brown wire from the ignition, 0.7v at the relay. 

I also ran a test out of curiosity to see if the lights would work if I plugged them straight into the circuit, without the relay. No dice on l or r. All new bulbs. When the relay is plugged in, I'm reading the same 10.6v from the l terminal as the brown wire. 

In other news, would these grounds here be actually hooked up to anything? It goes ground to washer to rubber gasket--- I'm assuming no, as there's nothing touching the fork on the other side either. Both me and the PO might have done a stupid hooking these up.

You can test the grounds with your voltmeter, connect black lead to battery ground and red lead to the "ground" side of the lamp units, anything more than approx 0.3v when the blinker switch is operated shows a poor ground (carry out measurement with everything connected)