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Thread: Tachometer issues

  1. #1
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    Default Tachometer issues

    I'm new to the group and this is my first post.I'm having issues with the tach in my 1988 Thunderbird Sport 5.0 (analog gauges).I replaced the voltage regulator on my cluster and after that my tach barely moves.At 45mph instead of showing 1500rpm,its not even at 1000.I put the stock regulator back in and no difference even after resetting the computer.The TFI module is new as is the coil so they aren't the culprits.I figure its the wire going to the computer.The coil to cap wire itself is 3 years old (Ford 9mm Racing Wires)and the car runs alright otherwise for 219,000+ miles.I just dont feel like tearing into the computer,especially with no garage and freezing weather lol.If anyone has any idea what it could be,i would appreciate some input.I originally replaced the regulator because my oil gauge was always reading low and i had read an old regulator could give false readings.Because i know someone will ask why i tried changing it

  2. #2
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    Make sure your connectors are seated tightly into the cluster.
    1988 Thunderbird 5.0
    GT40P, TFS-1, KB domes, 30#, MAF conversion, Explorer GT40 Upper/Lower, Smog delete, Wide Ratio AOD Mod, Unlocked Speedo, 3G Charging System Upgrade, Hi-Torque Mini Starter, 3.73 LSD, BBK 1 5/8 unequal headers, H-Pipe.

    88 Thunderbird/Cougar EVTM
    (Thanks to Trinom for hosting)

  3. #3
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    At 45mph you should be about 1200rpms, 1500 rpms would be about 60mph highway.
    Quote Originally Posted by jcassity
    I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
    Hooligans!
    1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
    1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
    1986 cougar.
    lilsammywasapunkrocker@yahoo.com

  4. #4
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    Go back over your connections, snug the three nuts on back of cluster that make the connections to tach...

    As far as computer, has zero to do with tach operation...






    My other rides (that actually do run & drive)

    1969 Fairlane Cobra 428CJ 4-Speed << New 49th Birthday Picture

    1972 Comet GT - 306 C4

  5. #5
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    The 88 EVTM doesn't show the analog tach for the 5.0 sport.
    The Turbo Coupe analog tach does not use the IVR (instrument voltage regulator) or, as Turbocoupe50 says, the computer.

    Turbo Coupe cluster connector C285 uses pins 1, 16 and 12 for the tach
    Pin 1 circuit #640 R/Y is power from fuse 16.
    Pin 16 circuit #11 DG/Y is from the Tach side of the coil.
    Pin 12 circuit #57 BK is ground.

    The Sport cluster connector has the same circuit numbers and color codes on pins 1, 16 and 12.
    My guess is it works the same as the Turbo Coupe.

    OOPS!!! I put the red box on pin 17, it should be on pin 16 for the Turbo Coupe connector.
    Attached Images Attached Images
    Last edited by softtouch; 01-01-2018 at 01:56 PM. Reason: red box on wrong pin#

  6. #6
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    Quote Originally Posted by softtouch View Post
    The Sport cluster connector has the same circuit numbers and color codes on pins 1, 16 and 12.

    My guess is it works the same as the Turbo Coupe.
    Yep, I have a '88 Sport tach in my original TC cluster...

    If fact only differences in the motor & Sport tach are one resistor and the faces...

    Note this is for '87 & '88, earlier Turbo Coupe tachs have entirely different circuitry...






    My other rides (that actually do run & drive)

    1969 Fairlane Cobra 428CJ 4-Speed << New 49th Birthday Picture

    1972 Comet GT - 306 C4

  7. #7
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    The only reason bring up the computer is because the yellow/green wire off the TFI runs to the relay off the computer.I had read elsewhere that if its making a bad connection (wire possibly exposed and grounding out)it can affect the rest of the electronics related to the ignition, which in turn sends the signal to the tachometer.

  8. #8
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    I took the tach apart,cleaned everything up,and finally got it working properly

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