Blowing signal 10A Fuse when I press down on the rear Brake

[lettle]

Here is an odd one gents.

Tonight when I was checking the bike over. I pressed down on the rear brake, I notice that the rear lights and the headlight dimmed a lot, more then usual. I pressed down again and blow the 10A signal fuse. I replaced the fuse and press the front brake the brake lights came on as per normal.

At this point I pressed on the rear brake pedal, blow another fuse.... Replaced the fuse again. I thought it was my brake switch. I jumpered the Green/ Yellow to the Brown wires for the rear brake switch. Turned the bike back on, the light were dim. I switched the bike off again before the signal fuse blow.

I measured the Green/ Yellow wire from the rear brake switch is it is going to ground. I unplugged the rear light connector, no change, the Green/ Yellow is still going to ground.

Has anyone seen this before? Any ideas?

Thanks,

Lawrence
1984 XS650 5V5 Stock

 

[Orion61]

You have a Short somewhere in the wire, you are going to have to trace it down. If you disconnect that wire and run a jumper wire it will prove it.
Due to vibration I have seen some pretty strange wear/rub damage to wires. ESPECIALLY around the headlamp bucket.
Let us know when you trace it down.
Cousin Larry

 

[lettle]

Well, I made some more progress tonight. I thought the issue was in the stator wires because replaced the shift shaft a few days ago and I thought I may have pinched the wires. I inspected the wires for any damage, did not find any and rewrapped them.

This here is the odd part:

**When front brake brake switch hooked up - The brake lights come on when the front brake is pressed, when the back brake is press the lights dim and there a a MAJOR current draw.

** When the front brake switch is disconnected - When the rear brake is press it works just fine.

Is there a diode in the system any where?

Any ideas would be greatly appreciated,

Lawrence
84 XS650 5V5

 

[nj1639]

Wiring sounds correct......brown to brown and yellow to green/white........ try ohming the green/white to ground and see if it tones just for laughs.

 

[Orion61]

When exactly did it start to do this? If it was fine before then it has to have something to do with that.
have you tried putting the old part back on?

 

[B Burdine97]

Yeah Id ohm out the wires or do a continuity test to make sure you have continuity. Something is creating an excess draw on the system but Im not sure what. Its strange this only happens when the rear pedal is depressed. Did you check all connections themselves? Making sure there is no corrosion in the system. Corrosion can cause an excess draw on the system, which could explain your dimming lights. Also check the bulb to make sure it is seated properly and that the terminals are clean. Like Orion61 said I think you have a short, but if you had a short Id think it would trip the fuse almost immediately, rather than dimming the lights and then blowing the fuse. Could be wrong.

 

[5twins]

The rear brake light switch is pretty simple and easy to take apart and inspect. Unhook the spring from the plunger and everything just pulls out the back of the switch. Both brake light switches are just a break in the power wire running to the brake light. When off, the power doesn't flow through to the light. When on, it does. The G/Y shouldn't run to ground. I think that's your problem.

 

[lettle]

Update.

I could not find the cause of the blowing fuse so I removed the rear brake switch and moved on to the next problem. Fast forward to today, I thought I would investigate more about the blowing fuse. I reinstalled the brake switch to test and now it works as it should and not blowing the fuse. Very odd and off putting.

Lawrence

 

[retiredgentleman]

Yes electricity is a strange beast. You have it working for now, but if there is a bare wire or connector, lurking somewhere, it will likely
show up again.

 

[XSLeo]

A good chance you moved the shorting wire when you removed/reinstalled the brake switch and is no longer shorting. If the reason it was shorting out isn't found it will short again. It may take years to happen but it will happen.
Leo

 

[DanielBlack]

You can try to force the fault by holding the brake down while wiggling wires.

 

[fredintoon]

Hi Lawrence,
your problem is an intermittent short circuit in the wire from the rear brake switch to the rear brake light.
Check the whole length of that wire for worn-through insulation and anywhere the wire could get squished.
First place I'd look would be under the seat where the rear brake wire plugs into the 2 into 1 connector with the front brake wire.
Those particular rear light feeds are vulnerable to being trapped under the seat but you really gotta check every last inch of wire to find the problem.