CX500 taillight/ plate light : SOLVED

Ok, I'm baffled, & I hope the electrickery experts here can help me see the light (pun intended). 1980 Honda CX500 Custom, custom...

I have replaced my stock "giant plastic box" brake/ taillight with an aftermarket brake/ taillight & separate license plate light, all LED. Tested before & after mounting w/ test leads, polarity correct, etc., & I spliced the factory bullet connectors to the new lights so I could keep the factory harness intact. The separate plate light hot lead is connected to the taillight lead, so should be getting power anytime the taillight is energized. Everything then connected to the harness securely.

Connect the battery. Key off - no lights. Key on (middle position) - dash light (N) on, taillight on, plate light OFF. Key at Park (3rd) - N light off, tail on, plate light ON.

The taillight & plate light are getting power from the same source wire in the harness (brown) - how can it possibly energize one lamp & not the other? And then light both in the other key position? I'm at a loss....

I'm sure there's something I'm missing, but my simple bean cannot puzzle out what it might be. I know that someday it will quit raining & the swamp that is my yard will dry out enough for me to be able to wheel this thing up out of the basement & onto the road & into the wind again. Lighting is the last hurdle before tags & inspection.

Thanks in advance for any & all help & suggestions-

Randy

Re: CX500 taillight/ plate light

Do you have a pic of the connections or a diagram of your wiring?

Re: CX500 taillight/ plate light

Sonreir-

Hey, thanks for getting back to me. Sorry I haven't been on the forum for a bit. I don't have a diagram of my modifications, but I might could come up with something. Basically I have the new taillight leads & the plate light leads wired to the brown harness wire, & the brake leads wired to the green/ yellow. I'll be with the bike again this week, so I can try & get some pic's.

BUT, I do have an update:
What I thought was just taillight was actually the tail & brake alternating as I cycled the key between ON & PARK. (I couldn't actually see the taillight, & was just seeing the light reflected on my hand. Once I removed the seat/ taillight ass'y & turned it around so I could actually see the individual elements lighting up, I realized my mistake.) So I actually have taillight (& plate) with the key ON, & brake light on (& no tail) with the key at Park.

So now my question becomes - why is my brake light hot when the key is on P? I could see it if one of the switches was closed, but then it would be on with the key ON as well, no? Like I say, I'll be with her again this week, so I'll do some more playing around & see if I can get more diagnostic with it now that I can see what's actually going on. BTW, the front brake switch is new (new lever/ master cyl.), & the rear switch was a known working unit at the time of disassembly.

Rather frustrating not being able to figure out what's happening, & not having the time to stay with it & pound out a solution. On the bright side, it's still raining every 2nd & 3rd day, so I may never be able to get the poor thing out of the basement anyway....

Thanks again for [hopefully] helping me puzzle this out-
r

Re: CX500 taillight/ plate light

Hard to say without seeing the full setup, but it sounds like something is miswired. Brake wires and running light swapped? Something like that?

That's why I was hoping for a diagram.

On the harness side of your bike, brown is running light, green/yellow is brake, and green is ground.

Re: CX500 taillight/ plate light

I'll dig into my old cx stuff to see if I can help, I think I have a stock harness and tail light around.

Well, you hit it on the head, Sonreir. A couple of the wires were switched under the seat - apparently mislabeled when I assembled the taillight unit. It took me a couple tries to get the right combination, but it seems to have gotten itself sorted.

Once I got the taillight working when it should, I also found that the rear brake light switch was shorting inside, keeping the circuit closed (most of the time).

Now, if I can get my seat back on without pinching or breaking anything, I may be good with lights. Then fill & bleed the front brakes, & mash all the wiring back into the headlight bucket, & she might be ready for the road....

Thanks again for the help!

r