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XJ650J Tach and Dash Lights Not Working

Discussion in 'XJ Technical Chat' started by Dan Gardner, May 6, 2022.

  1. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Got back out to do some testing today.

    Also now, just because screw me, the headlight isn't working.

    Getting no voltage at the following:
    Dash lights
    Tach
    Hi beam indicator
    and now headlight

    Just for grins, I tried swapping the diode block. No change.

    I'm almost ready to start removing the harness so that I can inspect every wire, inch by inch. Maybe my wife hired some rodent to chew on the wires in order to sabotage the bike or something. Anybody got a better idea?

    Also, what is the tape called that you are supposed to use to repair/create wiring harnesses?
     
  2. XJ550H

    XJ550H Well-Known Member Premium Member

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    Wire Harness Tape:
    Factory wire harness bundles were taped with a black electrically-insulating protective VINYL ELECTRICAL TAPE WRAP to provide both an orderly routing of the main harness wires and for additional wire protection. We have the correct 19mm wide black, high-voltage, adhesive-backed, all-weather stretch tape to allow you to repair or re-tape your harness. NOTE: XJ750 Maxim models that used this hard-shell, plastic ribbed tubing to protect the wire bundles had the hard-shell tubing externally wrapped with this tape.
     
  3. Rooster53

    Rooster53 Well-Known Member Premium Member

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    You could do that, but it might be better to know what you are looking for just in case there is not an obvious break somewhere

    So dash lights, high beam indicator, and and headlight power is from the headlight relay.

    That's not specific enough to really help out. We would need to know specific points for no voltage.

    Try the tach:

    With the key switched to on at the 4 pin connector do you have 12V at the Br wire in repsect to chassis ground?
    No - look for open signal fuse line
    Yes
    Do you have 12V at the Br wire in respect to the B wire on the 4 pin connector?
    No - look for open ground wire in main harness
    Yes
    Tach is defective or missing iginition signal - verify ignition signal

    Dash lights, hi beam indicator, headlight - activate headlight cirucuit as directed in post #10

    Do you have 12V at either the Y or G wire on the headlight H4 connector in repect to chassis ground?
    No - troubeshoot headlight relay circuit malfunction or open wire / switch
    Yes
    Do you have 12V at either the Y or G wire on the headlight H4 connector in respect to the B wire on the H4 connector?
    No - look for open ground wire in main harness
    Yes headlight should be illuminated, verify bulb
     
  4. XJ550H

    XJ550H Well-Known Member Premium Member

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    yamaha runs a ground wire then crimps on feeder grounds.

    they do the same thing for the brown power wire from the key to split off for the fuse box
     
  5. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Update: I spent some time combing over the harness. Checking and double checking every connection, and looking for any signs of damage. I had the harness out of the bucket and pretty much ready to remove. Then I hooked up everything again (outside the bucket). No change. Then I re-checked everything AGAIN and found the headlight circuit fuse blown. Replaced that fuse and all the sudden got my headlight, dash lights and high beam indicator back.

    The tach still didn't work, and the TCI was still toast (only firing on 1&4).

    Got out the DMM again, and now I'm getting voltage to the tach - that's a lot better. Swapped out a known good TCI and still no tach.

    I'm now assuming that tach is bad - maybe I blew it up by miswiring something, maybe it got messed up when out of the bike over the winter. Who knows?

    I'm also 99% sure that the TCI is bad, since I can swap it out and it will run on all 4. Also, the "good" TCI doesn't make the tach work either.

    I have a "new" tach on the way, still looking for a replacement TCI.

    What happened? Not sure. A few possibilities that I can think of:
    1. The fuse was sketchy all along, and my tinkering managed to fry the tach and TCI. I could have sworn I swapped out that fuse on day 1, but maybe not.
    2. When putting the thing back together this spring, I connected something incorrectly, which caused the tach to fry and some lights not to work, and then later I fried the TCI by trying to run it without a ground connected. Somehow then managed to blow the fuse while testing (not surprising, could have easily shorted something out and blown it). Carefully reconnecting and replacing the fuse results in a "fix" of most symptoms, except for tach and TCI.
    3. There was and still is a fault lurking inside the harness somewhere, and just jiggling and moving the harness "fixed" it for now.

    My money is on #2.

    I've got some work to do while I wait for the tach to show up - I've got a rebuilt caliper and master cylinder to swap out, along with all new brake lines. My 1&4 coil also reads 0 Ohm on the secondary side, so I'll replace that (although it obviously still works).
     
  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    the tach works off of the spark on 1 of the ignition coils if you are not getting spark on cylinder 2 and 3 the tach is not going to be picking up the signal from that coil pack as it is not firing 2 and 3
     
  7. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    I had hoped that the tach would start working when I swapped to the TCI that actually fired 2/3. But no luck.
     
  8. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    OK, still don't know exactly what happened with the lights, but had a huge facepalm moment today.

    Tach was wired incorrectly. When I took it apart I marked where the black and brown wires went, but I marked them wrong. So when I put it back together, I put it back correctly as far as my markings were concerned. But that was incorrect.

    For future me or anyone else, here is the correct wiring of the tach:
    20220521_225040018_iOS.jpg
     
    Rooster53 likes this.

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