Dead Tach on an '86 K75C

Discussion in 'Old's Cool' started by Jman, Jun 23, 2004.

  1. Jman

    Jman a.k.a. FUglyK

    Joined:
    Aug 27, 2003
    Oddometer:
    908
    Location:
    Land of Flat and Straight EH !
    Been experiencing a few minor difficulties with the beast most of which revolve around the instrument cluster and excessive amounts of rain. The bike had to sit outside for a couple of months and I think it has started to take its toll. :cry

    There was a moisture build up in the guages and the majority of lights and dials quit working on a ride last week. I have since taken the instrument cluster apart and cleaned it completely. All the instruments are back working as designed except for the tach. It does nothing. I am not an electrical genius by any means so I would welcome any ideas or places to start looking.

    I washed the bike yesterday and for a brief moment the needle did wiggle but promptly died and stayed dead. I assume it is a bad connection somewhere but am not sure where to look. All the connections seem clean and tight on the gauge pack.

    Any idea's? :ear

    Thanks.
    #1
  2. jdiaz

    jdiaz .

    Joined:
    Feb 27, 2002
    Oddometer:
    32,328
    Location:
    Flyover State
    The problem is inside the unit. There are usually separate plugs which connect to each of the speedo and tach units, and these things wiggle out over time. Sometimes you can put a piece of foam on the connector body to bridge the distance between it and the inside of the back cover, which will keep it securely plugged in. This would be my guess, especially if everything else is working fine.

    Jon
    #2
  3. Jman

    Jman a.k.a. FUglyK

    Joined:
    Aug 27, 2003
    Oddometer:
    908
    Location:
    Land of Flat and Straight EH !
    Thanks Jon, I had a feeling you would reply. :thumb The plugs felt quite solid into the back of the gauges but I will check that again and see if that is the problem.

    I was also wondering where the signal is picked up from the motor and if the connection could be loose at that end. I will try the connector tonight and let you know.
    #3
  4. jdiaz

    jdiaz .

    Joined:
    Feb 27, 2002
    Oddometer:
    32,328
    Location:
    Flyover State
    I'm guessing the signal for the tach comes from the FI box underneath the seat, but that's a SWAG. I've led a seriously charmed life when it comes to K bike instrument clusters, so I have minimal knowledge about it.

    Jon
    #4
  5. weezl

    weezl Sinical Optimumist

    Joined:
    Dec 15, 2003
    Oddometer:
    39
    Location:
    Soggy, Washington
    Here is one approach that may work - based on the above I'm not sure which plugs you're talkin' about:

    1. Remove instrument cluster from bike
    2. Unscrew back plate from instrument cluster housing - the entire black plastic back is held on by 6 or so screws.
    3. Unplug electrical connections 'inside' of cluster housing, at back of instruments.
    4. Carefully clean and reattach. Replace back plate of cluster housing.
    5. Take some quality electrical tape (the kind that stays flexible in the cold) and run a piece all the way around the cluster housing over the seam.

    Having done that on my '85 K100, it drastically reduced the intermittent wackiness of the speedo (I know you're prob is the tach, but same approach may work).

    G'luck
    #5
  6. weezl

    weezl Sinical Optimumist

    Joined:
    Dec 15, 2003
    Oddometer:
    39
    Location:
    Soggy, Washington
    Here is one approach that may work - based on the above I'm not sure which plugs you're talkin' about:

    1. Remove instrument cluster from bike
    2. Unscrew back plate from instrument cluster housing - the entire black plastic back is held on by 6 or so screws.
    3. Unplug electrical connections 'inside' of cluster housing, at back of instruments.
    4. Carefully clean and reattach. Replace back plate of cluster housing.
    5. Take some quality electrical tape (the kind that stays flexible in the cold) and run a piece all the way around the cluster housing over the seam.

    Having done that on my '85 K100, it drastically reduced the intermittent wackiness of the speedo (I know you're prob is the tach, but same approach may work).

    G'luck
    #6
  7. weezl

    weezl Sinical Optimumist

    Joined:
    Dec 15, 2003
    Oddometer:
    39
    Location:
    Soggy, Washington
    Here is one approach that may work - based on the above I'm not sure which plugs you're talkin' about:

    1. Remove instrument cluster from bike
    2. Unscrew back plate from instrument cluster housing - the entire black plastic back is held on by 6 or so screws.
    3. Unplug electrical connections 'inside' of cluster housing, at back of instruments.
    4. Carefully clean and reattach. Replace back plate of cluster housing.
    5. Take some quality electrical tape (the kind that stays flexible in the cold) and run a piece all the way around the cluster housing over the seam.

    Having done that on my '85 K100, it drastically reduced the intermittent wackiness of the speedo (I know you're prob is the tach, but same approach may work).

    G'luck
    #7
  8. weezl

    weezl Sinical Optimumist

    Joined:
    Dec 15, 2003
    Oddometer:
    39
    Location:
    Soggy, Washington
    Here is one approach that may work - based on the above I'm not sure which plugs you're talkin' about:

    1. Remove instrument cluster from bike
    2. Unscrew back plate from instrument cluster housing - the entire black plastic back is held on by 6 or so screws.
    3. Unplug electrical connections 'inside' of cluster housing, at back of instruments.
    4. Carefully clean and reattach. Replace back plate of cluster housing.
    5. Take some quality electrical tape (the kind that stays flexible in the cold) and run a piece all the way around the cluster housing over the seam.

    Having done that on my '85 K100, it drastically reduced the intermittent wackiness of the speedo (I know you're prob is the tach, but same approach may work).

    G'luck
    #8
  9. weezl

    weezl Sinical Optimumist

    Joined:
    Dec 15, 2003
    Oddometer:
    39
    Location:
    Soggy, Washington
    Here is one approach that may work - based on the above I'm not sure which plugs you're talkin' about:

    1. Remove instrument cluster from bike
    2. Unscrew back plate from instrument cluster housing - the entire black plastic back is held on by 6 or so screws.
    3. Unplug electrical connections 'inside' of cluster housing, at back of instruments.
    4. Carefully clean and reattach. Replace back plate of cluster housing.
    5. Take some quality electrical tape (the kind that stays flexible in the cold) and run a piece all the way around the cluster housing over the seam.

    Having done that on my '85 K100, it drastically reduced the intermittent wackiness of the speedo (I know you're prob is the tach, but same approach may work).

    G'luck
    #9