Spectre 750 Rear Tail Light/Brake Light Question

When I turn on the key, both the tail light and the brake light come on (both filaments are on). Depressing either the front and/or rear brake pedal has no effect on the lights. The bike was taken
apart during the resto process so it is possible that I reconnected the wiring up incorrectly to
the tail light. The turn signals work properly. The bike was apart for so long I don't remember if
the rear lights ever worked.

When the key is turned on should only the tail light filament light up? When the brakes are applied
should both filaments light up?

Any guidance would be appreciated.

With the key to the "Off" position(usually far left)the first click to the right to the "On" position should turn on the headlight and the running or tail light.

Color Codes On Most Kawasaki’s (written for 1980’s bikes)

HEADLIGHT:
RED with BLACK stripe, High Beam.
RED with YELLOW stripe, Low Beam.
BLACK with YELLOW stripe, the ground circuit.

BRAKE/TAIL LIGHT: Can be an # 1157 dual filament bulb
RED, Running or Tail Light.
BLUE,(sometimes with a Red stripe) Brake Light Circuit.
BLACK with YELLOW stripe, the ground circuit.

LEFT FRONT TURN SIGNAL: Can be an #1157 dual filament bulb
GREEN, Left front turn signal circuit.
BLUE, Left front running light circuit.
BLACK with YELLOW stripe, the ground circuit.

RIGHT FRONT TURN SIGNAL: Can be an # 1157 dual filament bulb
GREY, Right front turn signal circuit.
BLUE, Right front running light circuit.
BLACK with YELLOW stripe, the ground circuit.

LEFT REAR TURN SIGNAL: Can be an #1156 single filament bulb
GREEN, Left rear turn signal circuit.
BLACK with YELLOW stripe, the ground circuit.

RIGHT REAR TURN SIGNAL: Can be an #1156 single filament bulb
GREY, Right rear turn signal circuit.
BLACK with YELLOW stripe, the ground circuit.

never mind wrong info

I guess what I need to do is disconnect both tail light and brake light, turn on the key and check the
red tail light wire to see if I have voltage. What is happening now is that there is voltage on both
the blue and the red wires causing both filaments to light up. This could imply one or both of the brake switches is closed completing the circuit. I will need to look at the wiring diagram but I assume that the 2 brake switches which are wired into the blue wire are open when the brakes are not being applied. Depressing the brake lever closes the switch and completes the circuit.

If I disconnect the brake switches should I have current through the blue wire? I also need to verify that the wires going to the taillight are connected correctly. Looks like I need to sit down with the wiring diagram and my multi meter to try and figure out whats going on.

Disconnect one of the brake light switches and check for voltage at the rear bulb socket, and then do the other. You should not have any voltage on the brake circuit unless one or the other switches are depressed/squeezed.

almarconi,

Like Martin said above, check your rear brake light switch. My '75 z900, I just had to replace it about 2 months ago, was having the same type of problem you were, where the brake and running were both on. Took me a while to figure out, after testing everything, turned out to be the rear brake light switch.

I bought a new one, I think it cost about 4 or 5 bucks, I guess that's not too bad for a part that is almost 40 years old. Anyway, if you don't know what that switch looks like, if it's like mine, it should be by the drivers right foot peg, to the rear of it and up a few inches. It attaches to the frame and hangs upside down, with a long wire / spring comes down and attaches to the rear brake pedal.

Mine looked good, but upon further inspection, the poor old switch had just worn out and didn't have the strength anymore to pull up the plunger that the wire spring hooks up to, so both lights were on. That wire spring attaches to the switch, almost like a plunger that will go up and down when you depress the brake pedal and release it. Because it hangs upside down, when you brake it pulls that wire spring down which pulls the plunger down, when you take your foot off the brake, the little plunger pulls up, disconnecting the contact for the brake light. It doesn't travel very much, so work the brake pedal and watch that plunger, see if it pulls back up after releasing the brake.

If you already know about the brake switch, just ignore my rambling on about it and I apologize.

Like Martin said above, check your rear brake light switch. My '75 z900, I just had to replace it about 2 months ago, was having the same type of problem you were, where the brake and running were both on. Took me a while to figure out, after testing everything, turned out to be the rear brake light switch.

I bought a new one, I think it cost about 4 or 5 bucks, I guess that's not too bad for a part that is almost 40 years old. Anyway, if you don't know what that switch looks like, if it's like mine, it should be by the drivers right foot peg, to the rear of it and up a few inches. It attaches to the frame and hangs upside down, with a long wire / spring comes down and attaches to the rear brake pedal.

Mine looked good, but upon further inspection, the poor old switch had just worn out and didn't have the strength anymore to pull up the plunger that the wire spring hooks up to, so both lights were on. That wire spring attaches to the switch, almost like a plunger that will go up and down when you depress the brake pedal and release it. Because it hangs upside down, when you brake it pulls that wire spring down which pulls the plunger down, when you take your foot off the brake, the little plunger pulls up, disconnecting the contact for the brake light. It doesn't travel very much, so work the brake pedal and watch that plunger, see if it pulls back up after releasing the brake.

If you already know about the brake switch, just ignore my rambling on about it and I apologize.

I will check the rear brake switch.

By the brake switch failing, the circuit would remain closed and the tail light would remain on.

If I disconnect the rear brake switch, should the brake light go out?

It should, but unless there's a cross connection, or wires are plugged in where they shouldn't.

almarconi wrote: ...If I disconnect the rear brake switch, should the brake light go out?

Link to downloadable wiring diagram in KZrider FILEBASE:
www.kzrider.com/filebase/doc_download/285-z750n1

Front brake switch -- feeds battery positive from "hot" brown wire through blue wire to rear bulb's brake filament.

Rear brake switch -- feeds battery positive from "hot" brown wire through blue wire to rear bulb's brake filament.

Each switch is independent of the other.
Current fed through either switch should cause the rear bulb's brake filament to shine.
Disabling either switch has no effect on the other switch.

If I disconnect the rear brake switch, should the brake light go out? -- only if the front brake switch isn't simultaneously activated (i.e., connecting brown to blue) and thereby independently causing the rear bulb's brake filament to shine.

Good Fortune!

I had a chance to work on the bike this weekend. Disconnected the blue wire at the tail light and the running lights worked (only one filament is lights up). Reconnected the blue wire and both filaments light up. Disconnected the rear brake switch at the connector and one filament lights up. Apply front brake and both filaments light up. So now the front brake is working. Looks like bull durham was correct the rear brake switch was the problem. When I reconnected the rear brake switch both filaments light up regardless of the brake pedal being applied. I will see if I can take the rear switch apart and clean it. If not I'll just replace it. I also noticed that my charging system works better now, I could not get about 13 volts at the battery. Now with only one set of filaments light up the battery voltage is closer to 14 volts. Thanks for all your help.

almarconi wrote: ... will see if I can take the rear switch apart and clean it. If not I'll just replace it....

Might simply require an adjustment in mounting position of rear brake switch.



Good Fortune!

I was able to clean the switch with some contact cleaner. The switch is mounted horizontally and does
not have a spring attached to it. The plunger moves in and out, contacting the brake lever. It works good now.