GS500 Electrical problem

[FJCharlie]

thanks for responce.
i have 91 gs500, no mods were done-that im aware of.
left or right turn signal on headlight is dim, brake without turn signals-same thing, when combined way dim...
will make sweep through headlight harness, tnx for this one 
first i thought it was headlight bulb so i changed it-no fix
i will use wd 40 on all contacts and report if breaktrough

[cpaiin]

The same issue also happens to me.  Your problem could be totally different since I'm not sure how dim your headlight can get, but I always assumed this was normal.  It's hardly noticeable for me, and doesn't affect my ability to see while riding at night.  I gathered that the increased amount of power (going to the turn signals and/or brakes) just created less power to the headlight.

[the mole]

FJ, +1 to applecrews comments. If the standard 20 amp fuse is blowing you have a short circuit somewhere, if you keep trying bigger fuses eventually the wiring will act like a fuse and burn out.
If you know how to use a multimeter to trace the fault, go to it, otherwise start having a very close look at all the wiring (particularly blinkers by the sound of it) looking for frayed/chafed cables. Most likely ares are where there is movement or sharp edges, like around the steering head or where wires go through the headlight shell. Your bike is old enough for this sort of problem to occur due to old insulation getting hard/brittle.

[FJCharlie]

thanks guys for trying to help.
i noticed this first on my tach and speedometer, like new year decoration. afterwards i saw its also diming (is that a word?) my headlight, its a tiny little bit but noticeable.. i will record a video of this and post it. my fuses melt because they are plastic ones. but from time to time lets say a month  or two it blows. i rode 2000km in 15 days trough balcan countries with no problems, was riding for several hours and nothing happened to the fuse. 20amps, then i tried 25 and it was ok no dim and stuff, but now its happening again. i will check cables, i saw someone was using duct tape alot...
any other ground wires other than 2 on the right side of the motor?

[adidasguy]

All the fuses are plastic. They should never get hot enough to melt the plastic.
You have a problem. 20 amp is big enough for the fuse.
Somewhere you've got electrical problems. You need to take the wiring diagram and start tracing your wiring harness. Somewhere wires are either shorted, corroding or melting together.
On a proper bike, with all electronics working properly, no bad wiring, good battery,  the headlight should hardly ever change brightness except when the starter motor is engaged (it eats lots of power).
Sounds like you have a short somewhere that's sucking power, causing the fuse to get really hot almost to the point of blowing so it starts to melt. Then once in a while you pull a little over 20 amps and the fuse finally goes.

A fuse wire is a small heating element. As current flows through it, it heats up. At the 20 amp point, it heats enough to melt the wire inside. That the plastic is melting means you're pulling near 20 amps all the time - which is not what your bike should be using. Over 10 amps maybe to start it. After that, your bike should only be using a couple amps while running.

PS: If your wiring harnedd has lots of duct tape - someone has really fuggled it up.
Probably cheaper to buy a good used wiring harness for $10-$15 and replace the whole thing. On ebay, pinwall cycles is a really good, reliable bike breaker out of Ohio. Bought kinds of parts from them. Never had a problem, part always clearly photo'd and described,  and never been disappointed.

[FJCharlie]

here we go...
tonight when going back from work i recorded my problem...
tach lights are not as weak as shown in video...
http://www.youtube.com/watch?v=G2wwgKzCf-s

[adidasguy]

You do have an electrical problem.
Measure the voltage at the battery terminals. What is it....
1. With bike off
2. Bike turned on, not running
3. Bike running
4. Bike running with brake on
5. Depending on how fast your meter updates (if digital) it might be hard to measure the voltage difference with turn signals going, so brake light on should give an indication, but try with turn signals going.
6. How does voltage change if you rev to 4k RPM compared to idling at 1200 rpm?

You can also try doing same test measuring voltage somewhere on the front of the bike, like at the input to the high/low beam switch (or the connector to it) as that will be the exact voltage going to the headlight.

Possible the voltage regulator is going out and your voltage is high then drops down with additional load of the turn lights or brake light.

Another possibility is bad battery. Battery should act like a whopping big capacitor. With a slight change in load, voltage should not change.

[FJCharlie]

allready measured voltages when was checking for error. accu was brand new (used 12 and 14amp accus-so 2 in total), measured off and on state (idle) and at 5000rpm by manual. also measured alternator and rectifier/regulator at same conditions. it was all ok (manual has data about normal values)
thats the thing why i didnt give much attention to it. then i went to my mechanic, he thought its the ignition lock, he checked said its ok (ignition when faulty can eat alot of power), now i will open headlight and check all cables, but last time i was there it looked like 20 years old harness
you guys skip telling me if more ground wires on bike other than those 2 on right side of motor...
will remove tank seat and headlight and check all. hope for the best (i find a problem)
but im thinking ground wire is the problem, its attached to everything...
bike is running fine, lights off or on, but that dim/flash thing is anoying.. will post everything i do hopefully with good results.
addidasguy thanks for help