Elect wire continuity question

Duck749

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I have a '78 special I am rebuilding and installed a new MikeXS wiring harness. Through a few wiring diagrams I have all the wiring installed and what I believe to be correct. However one thing keeps stumping me at the reserve lighting unit. With the plug disconnected I am reading continuity between the black and black/blue wire. I show continuity from the blue/black to all the blue wires in headlight bucket. I think something is crossed in wiring or component bad. With all blue and black connections pulled in headlight bucket I do not have continuity between the black and blue/black in harness.

I don't think there should be continuity since it grounds other circuits. I can't get rid of the RLU because the ground issue between jumper would just keep headlight out.
 
So I have narrowed it down slightly, removed all blue wires in headlight and I am not grounding the blue/black out at the RLU. After one by one plugging in blue wires one of the blue wires to the light of the tachometer is grounded out. Could this be corroded bulb or something else shorted/fused together?
 
Yes still grounds out. Guess I am confused because I get you will see continuity across light bulb and fixture. However why is just the one wire which feeds two small tachometer lights feeding a ground signal all way back to wire in reserve light connector? None of the other lights or blue signals do this. Looking at the wiring diagram I do not think I should be seeing this continuity.
 
Yes still grounds out. Guess I am confused because I get you will see continuity across light bulb and fixture...

Maybe it's the bulb socket. I had one where the wiring chafed and shorted just inside the protrusion of the rubber boot. Had to slice open the boot and fix it.

Dunno about later models, but on the 70-71 instruments, the bulb boots and wiring have to set quite flat against the backside of the instrument, otherwise they'll lift the instrument and chafe against the mount base. My problem bulb/boot was the lower/left in this pic.

XS1B-TachBack02.jpg
 
The blue wires feed power to the instrument illumination bulbs and to the tail light, but they are fed from different sources. The tail light blue wire is fed from the ignition switch. The instrument bulbs are fed by the blue/black wire. So, you seeing a grounded blue/black wire indicates one of those instrument bulb blue wires is grounding (shorting) out. That seems to be what you've found. There's nothing wrong with you finding continuity between the blue/black and the blues feeding the instrument bulbs, it's supposed to be that way. But they shouldn't be grounding out.
 
Duck749,

If you are still stumped I have a 1978 Special sitting out in the garage that I also installed a Mikes wiring harness, that was one purchased many years ago but only installed this last winter/spring. I have had the bike running and everything seems to work fine.

If you could post a picture showing exactly the two wire you are having a question about I could check mine at the same location to see what my bike shows.

Note: I did find one mistake on the harness for my 1978. At least one of the wires going to the coils had the wrong end on it. Forget if it had a female where it should have had a male or the other way around. I know I changed one wire end and everything else worked out OK.
 
I also rewired my 1978 XS650 with a Mike's harness. I removed all the junk like the Light Checker, Reserve Ltg. Unit, Safety relay and the Flasher Cancel Unit. I got everything working except for the tachometer back lighting. Any ideas??
 
I also rewired my 1978 XS650 with a Mike's harness. I removed all the junk like the Light Checker, Reserve Ltg. Unit, Safety relay and the Flasher Cancel Unit. I got everything working except for the tachometer back lighting. Any ideas??
Well the tachometer back lighting should be the same circuit as the speedo-back lighting. I'd think they would join up inside the headlight shell.
 
The "HIGH BEAM, yellow", "TURN, blue pigtail", and "NEUTRAL, light blue" lights come out of the tachometer. The only other wire is a black "GRD", and a brown/black that goes back into the harness. I'll un-tape the harness and see where it goes. I suspect it is the back-lighting. I would love to have the running list for Mike's harness.
 
78 Rev counter has High bean and Neutral light + gauge lights x 2............

Hi beam, Y & B, (Yellow and black), and neutral light, Sb & Br, (Sky blue and Brown), go into a small 4 pin female connector.

Gauge lights, L & B, (Blue and Black), these are male bullet connectors and the 2 wires split in the sheath and come out as 4 wires, 2 gauge lights, 1 L & B for each bulb.

.So you should have 2 black wires, one in the 4 pin connector and the other is a bullet connector
 
Thanks for reply. Unfortunely, mine has only two (2) pigtails; black ground and blue turn signal.
This is a picture of one on eBay. I only see two pigtails
 

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Blue isn't turn signal, it's the back lighting. The turn signal indicator light is in the center pod.
 
Here is a pic from a 78SE/79SF Rev counter.............Your pic doesn't have the indicator light in it???

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Crop Text IMG_0144.jpg Cop Text  Paint IMG_0143.jpg
 
Not on my 78. The pod is only for warning. I took all the useless junk off. I removed all the junk like the Light Checker, Reserve Ltg. Unit, Safety relay and the Flasher Cancel Unit.
tach.jpg
tach.jpg
 
Thing is you were saying one thing and posting a flea bay pic of something completely different to your set up claiming it was the same as yours...............Confusing...........hell yea
 
Your turn signal light will have a Dg , (Dark green), and Ch, (Chocolate) wires from the bulb and there should be an earth, (black) there as well.......
 
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