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1981 CX500C
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Discussion Starter · #1 ·
I just installed an led tail light on my CX500C (old taillight was taken off before I got it) and the brake light stays on and is unaffected by the front brake switch. Currently don’t have a rear brake switch as it was missing when I got the bike from my brother. I’ve already changed out the front brake switch and that didn’t change anything. I’ve also hooked it up to the old stock tail light and had the same results. I’m very new to motorcycles and took this on as a project bike to be my starter bike.

I’m not super smart when it comes to things like this but I’ve been learning a lot through the process so you may need to explain some things to me as if I’m an idiot for me to comprehend😬
 

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83 Honda GL650i Silver Wing Interstate
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Welcome to the forum

You said the front switch did not change anything I take it you unplugged the wires going to it?

You need to find the rear brake light switch wires and make sure they are not touching anything as a start.

If both the front and rear wires are not touching anything you will need to start checking the wiring for both to see if something is shorting it out.
Dave ----
 

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1981 CX500C
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Discussion Starter · #3 ·
Thanks Dave!

The light stays on when the switch is plugged in, unplugged, and when I tap the unplugged connectors together.

Are the front and rear brake switch wires connected at any point? I’ve followed the front switch wires all the way to the CDI didn’t find any place where they would intersect. Not sure what happened to the rear brake switch in the first place so I have no idea where it had been connected to.
 

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Is the LED light that you installed a combination brake and tail light? If it is a dual function light how have you connected the light; which colour wires of the bike harness connected to which wires of the light unit?
 

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1981 CX500C
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7 Posts
Discussion Starter · #5 ·
It’s a complete unit with turn signals, brake and day lights.

I’m pretty sure I have it wired up correctly. I even switched what would be the day lights and brake lights to see if I did have it wrong but was met with the same result.

I’ll double check tonight and post how it’s wired up.
 

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1981 CX500C
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473 Posts
The taillight should have 2 circuits controlling the 2 functions.
One circuit is for the Running Light. Generally, this has a lower brightness intensity.
The other circuit is for the Brake Light. This will have a higher brightness intensity.
Make sure you are not confusing the 2 circuits. Your description suggests you may have the Running Light circuit energized.

Suggest to disconnect the All-in-One light unit. Use a voltmeter on the individual wires on the bike. Find the 2 circuits for the taillight functions. Match these wires to the wire diagram for the All-in-One unit.

The wiring maybe FUBARd a bit considering the missing switch on the rear brake pedal.

In a nutshell, you'll have to run down the wiring circuits to sort things out.
 

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In the Honda harness the brown wire is for the tail light, the green with yellow stripe is the brake light.
 

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1981 CX500C
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Discussion Starter · #8 ·
In the Honda harness the brown wire is for the tail light, the green with yellow stripe is the brake light.
That’s how I have had it wired up. I switched it around as well just to see if the wiring was incorrect but had the same result of the brake light staying on the entire time.
 

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'84 CX650E that is evolving into a GL500
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Are the front and rear brake switch wires connected at any point? I’ve followed the front switch wires all the way to the CDI didn’t find any place where they would intersect. Not sure what happened to the rear brake switch in the first place so I have no idea where it had been connected to.
The wires for the front and rear brake light switches are connected but it is inside the harness so you would have to peel back a lot of tape to get at that. And AFAIK the wires for them don't connect to the CDI.

The rear brake light switch is mounted to the frame with a spring connecting it to a lug on the brake linkage It is near the right footpeg on most models but I believe the CX500C has it on the left as in the pic below. In the pic you can see the wires attached to the switch (inside a black plastic sleeve) running behind the passenger peg mount and up behind the frame so if it is missing the wires from the main wiring harness that the switch plugs into should be in that area.


BTW: Welcome to the forum and welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is about 4 decades old and may or may not have had all of the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage. You can also find a colour wiring drawing for your model and the Honda Wire Colors chart at the Wiki that can be useful for figuring out things like this.

I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel (old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet). If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for modern stainless braided ones (they last practically forever and double the life of the fluid). And don't forget things like the rad hoses and the boot between the engine and swingarm (they can crack on the bottom where you don't see it).
 

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1981 CX500C
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Discussion Starter · #10 ·
The wires for the front and rear brake light switches are connected but it is inside the harness so you would have to peel back a lot of tape to get at that. And AFAIK the wires for them don't connect to the CDI.

The rear brake light switch is mounted to the frame with a spring connecting it to a lug on the brake linkage It is near the right footpeg on most models but I believe the CX500C has it on the left as in the pic below. In the pic you can see the wires attached to the switch (inside a black plastic sleeve) running behind the passenger peg mount and up behind the frame so if it is missing the wires from the main wiring harness that the switch plugs into should be in that area.


BTW: Welcome to the forum and welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is about 4 decades old and may or may not have had all of the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage. You can also find a colour wiring drawing for your model and the Honda Wire Colors chart at the Wiki that can be useful for figuring out things like this.

I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel (old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet). If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for modern stainless braided ones (they last practically forever and double the life of the fluid). And don't forget things like the rad hoses and the boot between the engine and swingarm (they can crack on the bottom where you don't see it).
This is the unit that was installed on my bike when I had the wiring fixed up (link below). Haven’t been able to get a hold of the guy who did it to ask him but figured I’d see if any of y’all had any ideas on if it played any part in my issue. Both wires coming from the front brake switch connect to the two red wires shown in the picture in the link.

 

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1981 CX500C
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Discussion Starter · #11 ·
This is the unit that was installed on my bike when I had the wiring fixed up (link below). Haven’t been able to get a hold of the guy who did it to ask him but figured I’d see if any of y’all had any ideas on if it played any part in my issue. Both wires coming from the front brake switch connect to the two red wires shown in the picture in the link.

I’d also like to note, that if I unplug either of the brake switch wires from the red wires the light goes out.
 

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This site will tell you how the ignitech should be installed. Review the material and see how your installation compares.
 

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'84 CX650E that is evolving into a GL500
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19,242 Posts
AFAIK the only connection between the Ignitech and the brake light switch is that it is recommended to get the power for the Ignitech from the black wire (switched power) that goes to the rear brake light switch.
The wires to the brake light switch should be that black power wire and a green/yellow that runs to the light.
 

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1981 CX500C
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Discussion Starter · #14 ·
SOLVED!

After looking at the instructions in the link from Reclinedrelic, I found that the two red cables that run to the cdi should be connected to two separate ends of that black cable that runs with the brake switch. After peeling back some tape, I found that the green/yellow wire that had been plugged into one of the two red wires along with the black wire was actually the splice for the rear brake switch. So I unplugged it and just left the one black wire plugged in and it seemed to fix my issue. Not sure where the other end of the black wire is for the second red wire, but I’ll call it a win at this point since it’s functioning correctly now.

If my explanation makes no sense I can take some pictures and try to explain it all better.

Thank you all for your help! Learning the ins and outs of working on this bike has been a blast and I really appreciate the community y’all have cultivated here. Excited to be part of it!
 
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