Brake lt woes

:S

check the power wire to the light with one side of meter,ground the other lead to frame or negative post on battery.this will tell you the voltage youre getting.

that is the easiest way to find a voltage drop anywhere on your bike just keep the negative lead on your meter stuck in the negative lug of your battery and check power before and after any plugs or switches you have doubts about,no need to make it more complicated than it needs to be

Motor Head wrote:

Well part of that is to have you check the system voltage when running, at the battery, then at the tail light socket. If there is a drop in voltage of more than say .3 you have dirty connections or resistance in your switch and wires. Ground the same thing applies, there should be no resistance from your - battery cable and your ground at the tail light socket.
System voltage measured at battery,at over 3000rpm should be less than 15v.

there is no reason to check his charging system for a taillight not working,if he has 12v at his battery he should have the same voltage at his lights as long as his connections are clean and he has no broken wires(wires are the same whether or not bike is running)or jacked up switches.

Tried to get a verification of over or correct charge voltage.

mark1122 wrote:

Here is a recap of the problem .
my running light burned out and brake light kept working. i changed the bulb, thinking nothing of a burnt out bulb. now just a few rides latter, my bud stops me and say my rear running lt is out again, but the brake lt is good.
any suggestions as to where to start with this one. electrical is not my strong suit. come to think of it , i dont have a strong suite. Lol
I’m more of a jackass of all trades.



Ok i checked a few things. i have a 76kz900 with what appears to be 73 to 75 wiring, only 1 fuse.
wires to tail have good ground (0, Resistance)at wires leading to the light. i have not taken the light apart to check the bulb connections.
I only 10.2 v.at the red tail running lt wire. the bat has 12.7, and 14.7v when running.
i tested the voltage from the white fuse wire up to the ignition (key)switch and have 12.7 there. i am confused about tracing the wires back further. there are 4 wires in the block to the switch.white, red, blue, brown.the wht(power straight from bat) goes in and when i turn the key on it energizes a brown coming out.if i turn the key all the way right it energizes the red and i get 12.7 v to the tail lt.with the key in run and i turn on the running lt's , it energizes the blue at 10.5v. at no time does it energizes the red. the red at the tail gets 10.5 for the running lt. so at some point the blue at the key must join to the red for the tail lt? but i dont see that in the wiring diagram? the blue goes to the headlight switch.
at no time does the red at the switch get power?
it shows the red going directly to the tail lt.
the blue goes to the head lt switch .i dont understand the head lt switch power? the blue is on booth sides of the switch , but 1 side is actual a red that comes back to the blue.and a brown is on another terminal that leads to the kill switch.

red wire should be constant power to taillight when key is turned on,if you dont have 12v from the red wire coming directly from your ignition switch id say its a bad ignition switch

Motor Head wrote:

Tried to get a verification of over or correct charge voltage.

if hes getting 12v everyplace else but the taillight its not a charging issue.
if a customer calls me to say theyve got a dead plug in the bedroom and theyve got 120 coming out of the breaker feeding it im not gonna climb the pole behind the house and check the transformer :S

disconect the power wire only and run a wire directly from positive side of battery in place of it and see if the light comes on

Head bone connected to the-back bome,back bone connected to the -hip bone,hip bone connected to the-knee bone,knee bone connected to the--the--ass bone?- now hear the word of the Plummen.Hee-damn -haw.bj

Motor Head wrote:

Yes with it set to the same 20VDC scale as when checking the voltage, if it a digital, which it sounds like from your posts.
I know you've been checking and cleaning lots of connections, did you get a better voltage at the rear tail light Assy socket yet? How did the voltage drop at the junction block/ single fuse work out?
Oh and did you happen to measure the voltage at the positive side of your ignition coils?

i have 0 v drop across the fuse until i turn on the head lt. then i loose .2 v across the fuse.
i get full v from bat to motor so ground bust be good.
i have a 1.4v drop to the tail lt with head lt on.

plummen,
i have had the meter cliped to bat ground for all tests.
i get. 3 drop at head lt socket. but the head light is not on and drawing power when i have it unplugged for the test,off course.
Plummen. the issue at the moment seems to be v drop, when i turn on the head lt. i think the tail LT may be a vibration thing?

Can you get to the back side of the Ignition switch connector and test the same color wire coming from it to the tail light? Is there a drop like this still with the brake light as well, it goes from brown ignition switched through brake switches front and rear. That's why I asked the Coil + voltage as well, this will feed those to.
The drop on the fuse sounds oK with out the head light, and the head light connector won't show much of a drop with out the load of 4.5 AMPS or so being pulled by the bulb. The bullet connections are probably clean by now? And so it maybe looking directly at the Ignition and head lamp switches. The Ignition was suggested quite a while back by one of the members.

i ruled out the ignition switch a while back. i got no drop across the switch on less the hd lt was on.
I'll check the brown again. i think i had the same drop there?

It' just trail and err till you find the culprit, I can't read the stuff to well on that diagram at the top of this page. But I can see your 1 fuse, and some others. Look close at the Box that has the path of contact for the Ignition switch and the head lamp switch, they show which wires connect in the different switch positions. Check the in coming and out going volts like you've been doing. You'll get it and like I said everything will work better.