Topic: Rear stop switch

[AlekStooge]

Hi, this is not a stock wiring harness, but modeled after it. It's for a 78 CB550K. First time wiring a bike up.

I hooked up the battery, flip the switch, running light pops on. I push down the brake pedal and the fuse light goes red. I look at the 5 amp fuse looks ok but I get 10 amp same thing happens. I pop in a 15 just because and I unhook the spring at the brake connector (see below). I pull the stop switch with pliers and fuse goes out.



Now I look at the wiring. The brake light has three wires black(ground),red(running) and Yellow(brake). I tested the red and yellow earlier and the yellow made the bulb shine a bit brighter so I determined that it was stop.

At the switch it's stock colors so black to switched power and green/yellow to a 3 way junction consisting of another green/yellow to front and to yellow to the bulb.

What's going on?

[Eddiev]

Is the problem only happening with the switch to the rear brake, or also with the front brake switch?

[69cb750]

What's going on ?

Black wire is hot +12 volts, check with volt meter
When you pull front brake lever or step on rear brake lever Green/yellow goes hot +12 volts, check with volt meter.

[AlekStooge]

Only rear brake, front brake line isn't built yet.

[AlekStooge]

I pulled the bulb and the flints look alright. I have the whole area around the taillight heavily insulated.

I wasn't able to pull back the PVC tubing around the switch but I did check it for continuity, obviously it's good. I checked the wires if they are all connected correctly and they are. I'm not sure on how to test for voltage other than the battery. I looked through my motorcycle electric book but didn't find anything on test for voltage.

[Don R]

 If you're wiring a bike, at least make or buy a test light. Even an old bulb and socket will work to find the difference between hot and ground. On a honda with original wiring green is ground, striped wires are switched feeds and black is 12V hot with key on.

[Dolomite]

Check your grounds, when you pull the switch it's closing the circuit to illuminate the light.

[AlekStooge]

I'm suspecting it's shorting some where around the taillight assembly. I look at my ground wiring again as well.

[AlekStooge]

Well I found the problem but yet have to find a solution to fix it. I removed the taillight assembly so none of it is touching the bare bracket. I popped in a 5amp fuse and the bulb got brighter and the fuse did not break.

Forgive me for my ignorance but it's quite obvious where the short is. The brass housing for the wires is touching the bracket. It's a tight fit and the sleeving doesn't cover it completely.



I think what I will do is bore the hole out more. This is larger than my biggest drill bit. Another question can the screws that hold the assembly onto the bracket short the light out as well? I think not otherwise you wouldn't be able to attach it to anything metal.

[Dolomite]

Is there enough space in between the socket and the housing that the socket could be covered with an insulator like electrical tape?

[AlekStooge]

Is there enough space in between the socket and the housing that the socket could be covered with an insulator like electrical tape?

Like putting electrical tape on the socket of the bulb then putting it back into the housing?

[Dolomite]

Yes, or shrink tubing if you have a large enough size. Assuming that you found the short was from the socket contacting the housing.

[AlekStooge]

I'm a little puzzled. I pulled the wires out and I saw the yellow brake switch wire was loose...great. What surprised me was the black wire and red wire were going to the socket and the yellow wire was soldered to the body of the socket. It almost like it was a ground wire. Which doesn't make sense because it all functioned properly when I moved the taillight away from the frame?

[Dolomite]

Is this a stock or aftermarket tail light?

[AlekStooge]

Aftermarket taillight. I put the heat shrink on and it still shorted.

[Dolomite]

If you swap wires to make yellow ground does it function? If the yellow wire is disconnected does it function?
Is the light dual function?
If its still shorting that sounds like some part is still grounding through the housing.

[AlekStooge]

If you swap wires to make yellow ground does it function? If the yellow wire is disconnected does it function?
Is the light dual function?
If its still shorting that sounds like some part is still grounding through the housing.

It functions as a running light with yellow disconnected. I haven't tried swapping wires. It all works when the taillight is away from the frame but shorts when it touches. The screws are attached to the bracket which is attached to the bulb and socket and it's all metal. It's so stupid because that means you can't attach it to anything metal like a motorcycle.

[Kevin D]

the yellow wire was soldered to the body of the socket. It almost like it was a ground wire.

Alex, the yellow wire IS the ground wire. It's soldered to the case. That MAKES it the ground wire. If it had Honda color code wires it would be green, not yellow.

Either the red or the black is touching the case somewhere, likely inside the lamp socket.

Is this the taillight bulb? What kind of bulb? It looks like the filaments are touching the case?? and no glass bulb??

[AlekStooge]

the yellow wire was soldered to the body of the socket. It almost like it was a ground wire.

Alex, the yellow wire IS the ground wire. It's soldered to the case. That MAKES it the ground wire. If it had Honda color code wires it would be green, not yellow.

Either the red or the black is touching the case somewhere, likely inside the lamp socket.

Is this the taillight bulb? What kind of bulb? It looks like the filaments are touching the case?? and no glass bulb??

I'm going to put the yellow as the ground and try that out away from the frame. It is the taillight bulb. I'll have to see what kind of bulb it is. Here is a bulb side photo.

[AlekStooge]

It's fixed everything works. Thanks for your help all. What I don't understand is how the light worked previously with black being grounded