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Discussion Starter #1
I am very lost with this electrical problem. My 1982 Honda CM450E's brake lights work but not the tail light. My bike has a switch, on the left hand side of the back-light housing, that turns the tail light on/off but the on position does not turn my light on. However, when i press on the brake the light turns on . This wouldn't be a big problem but i do most of my driving at night. I have checked all the electrical lines, changed the bulb, checked to make sure no electrical lines were disconnected behind the head light housing, with only one line being slightly loose. The left turn signal was not connected tightly so it made false contact. Sometimes my front blinker would stop working causing my back blinker to just turn on without blinking. This issue has been resolved since it is now tightly secured and my left front and back turn signal actually blinks constantly when turned on. my assumption was that a disconnected line behind the front light housing might have caused the issue, but so far nothing. I have read something having to do with the break line getting stuck might be the cause of the problem, but i don't believe that to be the problem since my brake light turns on when the break is applied, or that it might have something to do with a fuse. I have tried locating some sort of fuse near the tail-light area and around the front light area but nothing. I have read the manual but this problem does not show any resolution. Could the switch on the tail-light be malfunctioning and therefore need replacing or is there a fuse that needs to be checked that i might have missed? I know this is very vague as an electrical system requires a lot of diagnostics but any ideas you can throw at me will be greatly appreciated.
 

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Pictures of the switch might help, sounds like a previous owner add-on. The tail light should be on when the headlight is on. The brake light is a separate element in the bulb, just as if it were a separate bulb.

Using a test light or multimeter/voltmeter check whether you have power going to the switch. If you do, the switch or associated connections are your problem. If not you'll have to trace it back to find out where you're losing it. The fuses are in a block behind the left side cover.
 

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Check the brown wire coming from the key switch. Had the same problem on my '82 CB450, a new key switch fixed it.
 

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Discussion Starter #5
Correct. I checked the fuse on the bike and the tail light fuse was burned out. The fuse is a 7A, same as front light, but i couldn't find that exact number so instead I'm using a 7.5A fuse. After replacing the burned fuse I noticed that the new fuse burns out as soon as i turn the tail light on. As you mentioned before most likely there is a short happening somewhere in the electrical system. The next step is to trace the cables and locate where the faulty wiring might be. Thanks for the help. I'll post anything I come across as it might help someone in the future.
 

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Check the rear inner fender. The wires for the tail light run in a channel. The brown wire may have shorted to the fender in/at that channel.
 
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