tail light

[Spargett]

I second the grounding. I had a hell of time getting my function consistently. I ended up making an extra ground on the rear tail light. Works perfect now.

[arch379r]

if i turn off headlight light switch and use rear brake the taillight comes on. At the same time the headlight comes on????

[Gunner_CAF]

I would check your ground wire under the tank. There there should ground wire from the wiring harness that should be connected to the coil bracket. It's possible this wire is broken.

We are working on a 73 CB500 that was had a lot of electrical weirdness. Different bike, different wiring, but strange stuff would happen when you put the switch in different positions. The tail light would come on in one position, the other it wouldn't, some things worked some didn't. I scratched my head over the wiring diagram trying to figure out where this ground connection was located. Should have figured it was in the same place as the CB77 :) We pulled the tank off and found this main ground wire broken, once fixed everything worked perfectly. When the common ground breaks, it backfeeds though the system in strange ways causing this type behavior.

Gunner

[e3steve]

if i turn off headlight light switch and use rear brake the taillight comes on. At the same time the headlight comes on????

Not enough information!

• - Are the taillight & headlight at full brightness or do both appear dim/subdued (assuming a fully-charged battery)? -- such a phenomenon would indicate a ground fault, as Gunner has suggested
  - Does the headlight filament light up or just the parking light?

For a more complete diagnosis please provide more of a full description, there's a good chap....


Woman says to doctor: "I have a discharge and it really smells horrible"
Doctor says: "OK, pop yourself up on the couch" and then proceeds to conduct a full internal examination. "How does it feel when I move my finger like this?"
"Very nice!" patient responds. "Now, about this discharge from my left ear......"

[teazer]

Something's not quite right there.

There are many ways to approach this but they all require a methodical approach.

First I'd add a small ground lead from the rear light bracket to the frame as a ground, then determine if all the switches and connections seem to match the wiring diagram and look OK. If it all looks botched, you have to go back to basics.

IIRC there ere a couple of versions of the wiring and switches, so you need to determine which you have. One IIRC has the lights ON-OFF in the main switch and the other has it in the headlamp switch, but I don't have either to test that theory. So start off by working out how yours is supposed to operate.

It is very possible that it has a wrong main switch. Check it against the wiring diagram. If unsure, ask one of teh guys here to tell you exactly what it should look like.

If it all looks kosher, first disconnect both leads to the tail lamp assembly and then start at the main (keyed) switch. Does it have three positions? Off, ON, and Park. Check the TL lead (white) in all positions. In Off, and IGN, there should be nothing there, but in park, it should have power. That lead is connected to the marker lamp in the headlamp.

Now shift the multimeter leads across to the brake light lead close to the battery (not the end connected to the light itself). With the switch in all positions, there should be no power there. Now press the brake pedal and repeat. there should be power in the ON position only -not the others.

With the T/L assembly still disconnected under the seat, apply +12V to the white lead to the tail lamp assy and -12v to ground and see what lights up and then repeat on the blue lead. the blue should be much brighter - It's the stop filament of the bulb.

If that all checks out but the headlight is coming on even when it's supposedly switched off, then the error is in the wiring.

With the T/L disconnected, check teh brake switch and follow its leads. It should have two leads- Blue to the tail lamp (stop filament) and black which is switched 12V.

[LOUD MOUSE]

I must say only that one statement may/could be correct for a quick easy fix.
Anyone know which one it is?. ........lm

Something's not quite right there.

There are many ways to approach this but they all require a methodical approach.

First I'd add a small ground lead from the rear light bracket to the frame as a ground, then determine if all the switches and connections seem to match the wiring diagram and look OK. If it all looks botched, you have to go back to basics.

IIRC there ere a couple of versions of the wiring and switches, so you need to determine which you have. One IIRC has the lights ON-OFF in the main switch and the other has it in the headlamp switch, but I don't have either to test that theory. So start off by working out how yours is supposed to operate.

It is very possible that it has a wrong main switch. Check it against the wiring diagram. If unsure, ask one of teh guys here to tell you exactly what it should look like.

If it all looks kosher, first disconnect both leads to the tail lamp assembly and then start at the main (keyed) switch. Does it have three positions? Off, ON, and Park. Check the TL lead (white) in all positions. In Off, and IGN, there should be nothing there, but in park, it should have power. That lead is connected to the marker lamp in the headlamp.

Now shift the multimeter leads across to the brake light lead close to the battery (not the end connected to the light itself). With the switch in all positions, there should be no power there. Now press the brake pedal and repeat. there should be power in the ON position only -not the others.

With the T/L assembly still disconnected under the seat, apply +12V to the white lead to the tail lamp assy and -12v to ground and see what lights up and then repeat on the blue lead. the blue should be much brighter - It's the stop filament of the bulb.

If that all checks out but the headlight is coming on even when it's supposedly switched off, then the error is in the wiring.

With the T/L disconnected, check teh brake switch and follow its leads. It should have two leads- Blue to the tail lamp (stop filament) and black which is switched 12V.

[e3steve]

Something's not quite right there.......

Teazer, you're teasing Arch! A great and full diagnostic approach...... BUT your (perfect, I must add) explanations assume that Arch isn't electro-diagnostically inept; and, thus far, his requests for help on the matter lead me to believe that he is -- no offence, Arch, but it's a very basic problem. And there's a simple solution that I'd expect one of my former apprentices to (theoretically) produce to me in less than 60 seconds.

So, one step at a time.

• 1. Have you tried the additional taillight grounding wire approach?
  2. Have you studied my colour wiring diagram (and do you understand/can you follow it)?
  3. Do you have a multi-meter and are you competent in its use?

Without answers to these Qs then we're all just shooting off in the dark.