Author Topic: taillight problems  (Read 782 times)

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Offline rickibrown

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taillight problems
« on: December 19, 2018, 08:13:59 pm »
Help needed 1975 cb550k1 stock harness with new reg/rec installed. Bike runs great, charges, headlight works as does turn signals and horn. Problem when front break applied 15amp  main fuse blows bike dies this is with rear brake switch disconnected. With ignition off plug in rear brake switch turn ignition same thing 15 amp main fuse blows? Both switches have black ( switched power). I cannot conceive of connection between main fuse inlign red wire which operates engine side and the black switched power light side. Any help welcome.

Offline jgger

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Re: taillight problems
« Reply #1 on: December 19, 2018, 10:02:13 pm »
I would think if you unplug both switches a and turn on the key it should not blow the fuse. If it does blow the fuse it has nothing to do with the brake light switches.

I believe the brake light switch is a simple grounding switch, someone smarter than me can verify that. So if there are 2 wires plugged in one should show continuity to a known ground and the other should not. If they both show continuity to ground then you have something  crossed in the harness. You might have the power wire plugged into the ground at the tail light.

Mind you I'm really stupid on electrical stuff and I may have just demonstrated that! 😦 or I may have nailed it.😒 so in the words of Dirty Harry "Are you feeling lucky, punk?" The good part is if I just gave you a bunch of BS it will encourage someone in the know to chime in and straighten BOTH of us out.

Anyhoo  get out the multi meter and start checking things. Good luck.
"The SOHC4 uses a computer located about 2-3 ft above the seat.  Those sometimes need additional programming." -stolen from  Two Tired

Offline calj737

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Re: taillight problems
« Reply #2 on: December 20, 2018, 04:17:03 am »
If you turn the key ON, and the MAIN fuse blows, somewhere you have that BLACK wire grounding out.

Aside from the Reg/Rec change, have you made any other modifications? Did this issue only surface after the RR swap?
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Offline rickibrown

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Re: taillight problems
« Reply #3 on: December 20, 2018, 07:20:29 am »
Thanks for input. To clarify It is not the ignition key that is blowing fuse it is when either the front brake operates the hydraulic switch or pluging in the rear brake switch. This bike was in a field for 20yrs with no covers on, lots of rot around connectors, so I added the new R/R and a sub harness, 2 pin relay. No resource to previous original condition. Bike runs great and is showing charge. I tend to agree that the black maybe ground out but how does that relate to 15amp fuse blowing.
This is my first rebuild and electrical my weakest area.

Offline rickibrown

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Re: taillight problems
« Reply #4 on: December 20, 2018, 08:27:17 am »
In addition I went with spade auto fuses the 15 amp has red/white to red When adding rec/reg I could see no other option is this wrong>

Offline calj737

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Re: taillight problems
« Reply #5 on: December 20, 2018, 09:15:54 am »
Thanks for input. To clarify It is not the ignition key that is blowing fuse it is when either the front brake operates the hydraulic switch or pluging in the rear brake switch.
So that still points to an issue with BLACK grounding out. It is the powered side of the BRAKE circuit.

From yuor description, it is very likely you have a chafed BLACK wire running along the frame, perhaps between the new RR and the rear brake switch, or from the front switch to the rear where it is spliced in the harness.

Going to have to lift the seat, pull the tank, and start carefully inspecting the wires to find it.
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*** Currently experiencing life at 60 WTFs per hour ***
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Offline rickibrown

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Re: taillight problems
« Reply #6 on: December 20, 2018, 04:19:17 pm »
Thanks will tear into it tomorrow and report back.

Offline scottly

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Re: taillight problems
« Reply #7 on: December 20, 2018, 06:03:06 pm »
Hi Ricki. First, this is the wrong place to ask questions. It should have been posted on the sohc bikes board.
The brake light switches both feed 12V to the light via the green/yellow wire. If that wire becomes shorted to ground, it will blow the 15 amp main fuse whenever either the front or rear brake is applied. A common place for this to happen is where the brake/tail light wires pass through the rear fender: there is supposed to be a rubber grommet to protect the wires from wearing against the edges of the hole.
Don't fix it if it ain't broke!
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Offline rickibrown

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Re: taillight problems
« Reply #8 on: December 21, 2018, 07:15:02 am »
Still cannot find short, if I turn on ignition my test light shows power at both ends of black, pressure switch and rear brake ( switched power )Is the green /yellow a neutral wire last comment is telling me its power? Under rear seat is fine have power thru brown to rear light but no illumination? The green ( ground ) 4 way at rear works fine for indicator light. The rear taillight ground is also plugged into 4 way. My feeling is this is 2 seperate issues.

Offline rickibrown

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Re: taillight problems
« Reply #9 on: December 27, 2018, 04:07:10 pm »
Rear led light switched wires ( weird colors ) everthing working fine. Except led taking full current so brake front and rear does not increase illumination.
I believe I need a diode /resistor kit. any links welcome.

Thanks again for all your input.

Offline scottly

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Re: taillight problems
« Reply #10 on: December 28, 2018, 08:07:50 pm »
No, you don't need diodes or resistors, you need to properly wire your aftermarket LED taillight/brake light. "Weird colors" doesn't help much. ;)
Don't fix it if it ain't broke!
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Offline rickibrown

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Re: taillight problems
« Reply #11 on: January 07, 2019, 08:07:21 am »
Resolved missed wired rear aftermarket LED - no direction no connectors
LED color first then harness. Black to dark green, red to green/yellow strip,
white to brown. Thanks.