Light electrical debug

Duck749

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ok, finally got battery in to sort out elect issues after new wiring harness, rebuild, etc. I installed all LED lights and see I need the new flasher unit from superbrightled.com, removed and jumped reserve lighting stuff, etc. Headlight works, turn signals work (minus flash as wait on part), brake light works and finally got starter to go after finding ground issue with handlebar start button.

Question I have which couldn't find nor am I familiar with XS650 on, if my headlights are on, should the rear running and liscense plate light also be on at same time (my assumption is yes)? Currently they are not and cannot get them "on" so thinking something is wrong in wiring. I wanted to confirm prior to chasing and pulling connectors. I tested all bulbs during install and rear running light is integrated brake light which I know works..
 
Blue wire from the ignition switch is power for the tail light and gauge backing lights...........The year of bike would be advantageous.......
 
1978 special.

With headlight on the gauges are also on, just liscense and rear running light are not.
 
When the key switch is in the ON position it sends power out on a blue wire to the tail light. It also goes to the Gauge lights.
At the tail light check for power on the blue wire. If no power trace it back till you find where it gets lost.
With a look through the "Some Electrical Diagrams" thread you will find one for your year. It comes in handy when you troubleshoot wiring issues.
Did you get your new harness from Mike's XS? Some have found issues with ones they got there. All the wires are the right color but they are sometimes in the wrong position in the plugs. Check at all your plugs to see that where a wire goes in, it plugs into the same color wire going out.
Leo
 
Yes got it at Mikes, I have clymer and some other misc diagrams online which looks like blue is common to feed multiple lights. Good info on harness as that helps what I have to do.
 
On this diagram it shows a Y/L, (Blue/Yellow), Gauge lights and Taillight power wire from the ignition.........I think the diagram maybe wrong and the L/Y should be L, (Blue).

78_XS650SE.PNG

This also shows the L/B going to the RSL, (Reserve Lighting Unit), connected to the L wire coming from the gauge lights.........I don't think these should be joined.

On Diagram.
L/Y coming from the ignition to the Light checker, (lights the red Tail light Fail light on the Tower), to L to tail Light
 
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So it looks as if the blue coming out of the new harness to tail/brake light is dead. Tried chasing but can't determine where it disappears to. Thinking I can steel power from the purple/black (in above diagram) at the safety relay since I get voltage on/off with the headlight switch. Did temporary wire and lights work as they should.
 
If you had the more complex 7 wire light checker and removed it, that's where you lost the tail light power. Power for the tail light runs through the light checker. The blue/yellow from the ignition switch feeds it in and the blue feeds it out to the tail light. If you remove that 7 wire light checker, you need to jumper the L/Y and blue together to restore power to the tail light.
 
In 78 they did some changes. They used a single fuse set up like the earlier bikes on some and the 4 fuse set up on others.
I'm not sure which models but my Clymer book says Early from serial number 2FO-000101 to 2FO-006501, Late after 2FO-006501.
Don't know if this helps. That maybe why some 78 bikes don't match the 78 diagrams.
Leo
 
'78 Standards had the single fuse, Specials got the 4 fuse box.
 
Mine had (rats nest) 4 fuse which was partial reason driving me to get a new wiring harness, which is also 4 fuse. I removed the reserve lighting module and left the light checker. I tied the two wires together as indicated on some forums. This morning I actually checked voltage there and its on/off with headlight so I tapped into that versus safety relay I mentioned earlier. Looks like everything is working now with headlights.
 
The '78 models had a couple electrical things that were unique to that year. They were the last year with a headlight on-off switch in the right handlebar control and the first year with the auto-on headlight relay. The handlebar headlight on-off switch was somewhat handicapped. It only functioned with the key on, motor off. Start the motor and that auto-on relay bypassed the handlebar switch, no matter what position it was in the headlight came on. If you'd like to restore full function to that handlebar switch so that you can control the headlight on-off function at all times, simply unplug the blue/black wire coming out of the safety relay .....

vG1TF6W.jpg
 
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