How to wire up a 504 Tacho
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  1. #1
    1000+ Posts Shobbz's Avatar
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    Default How to wire up a 504 Tacho

    I have now got myself a 504 tacho, thanks ray.

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    How do i wire it up?

    It seems to be wire through the connectors on the bottom of the cluster. As my car is not a Ti I am assuming that this won't work, nor do i want to try it in case it kills the tacho some how.

    There is one wire which i assume is for power, as its the same one as on the clock?

    Would I be wrong in assuming that you connect it to the positive of the coil and the negative of the battery? NOt sure which one would be which on the back of the tacho though.

    thanks

    shobbz
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    2005 407 ST Exec
    1975 504 GL

  2. #2
    Guru davemcbean's Avatar
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    There should be one on the back which connects to the same as the clock and another which connects to the dizzy side of the coil (or straight to the dizzy, take your pick).

    Dave
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
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    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  3. #3
    1000+ Posts Shobbz's Avatar
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    Quote Originally Posted by davemcbean
    There should be one on the back which connects to the same as the clock and another which connects to the dizzy side of the coil (or straight to the dizzy, take your pick).

    Dave
    Dave,

    There is the clock connection, but there are two other wires comming from the back of the tacho.

    This is a whole cluster I am putting in, not just the tacho so the tacho is currently wired to the cluster?

    Is this why there are two wires including the "clock" wire?

    Which of these wires? Might have a look see now and see if one is for a light or something like that?

    thanks

    shobbz
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    2005 407 ST Exec
    1975 504 GL

  4. #4
    Guru davemcbean's Avatar
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    Quote Originally Posted by Shobbz
    Dave,

    There is the clock connection, but there are two other wires comming from the back of the tacho.
    Hmm, sounds different to mine.

    Dave
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  5. #5
    1000+ Posts Shobbz's Avatar
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    Quote Originally Posted by davemcbean
    Hmm, sounds different to mine.

    Dave
    After looking at the wiring diagram, it looks like it connects to the regulator?????

    What would happen if i plug the cluster into the dash?

    Would bad things happen?

    thanks

    shobbz
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    2005 407 ST Exec
    1975 504 GL

  6. #6
    1000+ Posts Shobbz's Avatar
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    Quote Originally Posted by Shobbz
    After looking at the wiring diagram, it looks like it connects to the regulator?????

    What would happen if i plug the cluster into the dash?

    Would bad things happen?

    thanks

    shobbz
    Can I hook up A multi meter to the tacho? And test resistance or something????

    Just wonderign how I can get it to work?

    shobbz
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    2005 407 ST Exec
    1975 504 GL

  7. #7
    Tadpole
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    Default 504 Tacho wiring

    Run a wire from -ve side if coil to tacho . Use the power feed for the clock to provide power for the tacho. That's the two basics power and an impulse signal feed. Too many years to remember exactly what each looks like behind there. If I have time tommorrow will pull the cluster and have a look. Be warned that there is a small chance that due to age a faulty tacho can cause misfiring !! Had that happen Saw another post about optimax . Due to a small issue with comp ratio I always use it, however all high octane fuels contain detergents to clean fuel injectors on old engines this will dislodge large amounts of carbon. Keep to the basics valve clearances plugs and points keep timing standard, check comp ratio and vaccuum. Fuel can't perform miracles. Finally use an upper cylinder lubricant and BP Ultimate is the best.

  8. #8
    Fellow Frogger! Ralph's Avatar
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    Shobbz,

    One of the wires is probably for the light when you have the head lights on so you can read it at night. The other two operate the tacho.

    One wire should go to earth. This will be part of the car's body that is attatched to the negative pole on the battery (if not, it is probably incorporated into the instrument cluster's wiring). You can check for a good earth by setting your multimeter to ohms (W) and clamping one of the multimeter probes to the negative (-) post on the battery. The other probe should be placed on a good bright and shiny earth point where you want to put the wire i.e. a screw or bolt that goes through the bodywork. Your multimeter should read <0.3W.

    The other lead from the tacho should go directly to the coil. This wire connects to the negative (-) terminal of the coil. If you put it on the positive (+) side of the coil the tacho will read nothing. The tacho works by sensing the voltage drop (collapsing and building up of the electromagnetic field) across the coil as the points open and close. When the points are open you will get 12V at the negative side of the coil, when the points are closed you will get 0V.

    The negative terminal of the coil connects directly to the side of the distributor and passes through to the points.

    Matt.
    On the internet, no one knows that you are only wearing a fez.

  9. #9
    1000+ Posts Shobbz's Avatar
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    Quote Originally Posted by Ralph
    Shobbz,

    One of the wires is probably for the light when you have the head lights on so you can read it at night. The other two operate the tacho.

    One wire should go to earth. This will be part of the car's body that is attatched to the negative pole on the battery (if not, it is probably incorporated into the instrument cluster's wiring). You can check for a good earth by setting your multimeter to ohms (W) and clamping one of the multimeter probes to the negative (-) post on the battery. The other probe should be placed on a good bright and shiny earth point where you want to put the wire i.e. a screw or bolt that goes through the bodywork. Your multimeter should read <0.3W.

    The other lead from the tacho should go directly to the coil. This wire connects to the negative (-) terminal of the coil. If you put it on the positive (+) side of the coil the tacho will read nothing. The tacho works by sensing the voltage drop (collapsing and building up of the electromagnetic field) across the coil as the points open and close. When the points are open you will get 12V at the negative side of the coil, when the points are closed you will get 0V.

    The negative terminal of the coil connects directly to the side of the distributor and passes through to the points.

    Matt.

    Matt,

    You have confirmed what I was thinking, I just had no idea how to go about it.

    I think that you may be my new hero

    Will post results tommorrow.

    shobbz
    Previous
    2005 407 ST Exec
    1975 504 GL

  10. #10
    1000+ Posts Shobbz's Avatar
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    Quote Originally Posted by Shobbz
    Matt,

    You have confirmed what I was thinking, I just had no idea how to go about it.

    I think that you may be my new hero

    Will post results tommorrow.

    shobbz
    Maybe its the tacho. Connected it up, out of the car and the tacho reads ~2500 on idle, and will quite happily move to 4-5000 when i touch the accelerator slightly????

    Does it need a resistor in line??? or somethign similar. Does it need to be connected to the dash via the light lead to work????

    thanks

    shobbz
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    2005 407 ST Exec
    1975 504 GL

  11. #11
    Fellow Frogger!
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    Quote Originally Posted by Shobbz
    I have now got myself a 504 tacho, thanks ray.

    How do i wire it up?

    It seems to be wire through the connectors on the bottom of the cluster. As my car is not a Ti I am assuming that this won't work, nor do i want to try it in case it kills the tacho some how.

    There is one wire which i assume is for power, as its the same one as on the clock?

    Would I be wrong in assuming that you connect it to the positive of the coil and the negative of the battery? NOt sure which one would be which on the back of the tacho though.

    thanks

    shobbz
    Hi Shobbz,
    i put a tacho in my GL 504, and it just worked pretty much straight away. Put it where the non-working clock was, and it got it's reading from the little cluster of clip on thingys (forget what they're called) at the back. Then it was just a matter of conecting power to the tacho, which i did by taking the power from my crappy radio (just Am anyway).
    Now i want to put a Cd player in, so i have to run another lead off something else!
    Seems strange that yours says your car idles at 2500 though, not sure what would be doing that.

    Good luck,
    Andrew

  12. #12
    1000+ Posts Shobbz's Avatar
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    Just to be special i have in cluded a photograph of the tacho, as it resided in the instrument cluster. I haven't taken it out of this cluster and put it in mine yet.

    I tried putting this whole instrument cluster in and nothin worked, not even the lights, the bulbs worked in my current dash, so i guess the wiring is different.

    here is a picture, i just wanted to be special and put it up. The wires attached to the tacho are the ones that i used during testing. Maybe the whole cluster has to be earthed to the car for it to work, i don't know. The wire is just old dodgy speaker wire.

    thanks

    shobbz
    Attached Thumbnails Attached Thumbnails How to wire up a 504 Tacho-tacho1.jpg  
    Previous
    2005 407 ST Exec
    1975 504 GL

  13. #13
    1000+ Posts Shobbz's Avatar
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    I decided to have another muck around with the tacho this arvo. Its connected up with the right wires on the negative of the coil and a nice fresh earth point.

    Car still idles at ~1500rpm. I guess that one of the resistors has died.

    I will see if i can replace them and see how it goes.

    shobbz
    Previous
    2005 407 ST Exec
    1975 504 GL

  14. #14
    1000+ Posts Shobbz's Avatar
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    Quote Originally Posted by canjohn
    Dave,

    A comment about your observation on 504 tacho's:

    "I've noticed that the Peugeot tachos that I've had read a few hundred rpm faster than what you're actually reving (possibly due to incorrect needle fitment) "

    If you remove the tacho from its case you will find a small adjustable resistor on the printed circuit board inside. It will allow trimming of its response but you will need an accurate oscillator to calibrate it against.

    I tried to remove the needle but it is extremely well fixed to the shaft and pulling on the needle may damage the delicate movement supporting the shaft.

    John
    I found this in another post, I might have to try it. I had a quick look at the tacho but i didn't see this resistor.

    WIll have a look see tomorrow.

    shobbz
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    2005 407 ST Exec
    1975 504 GL

  15. #15
    1000+ Posts Wildebeest's Avatar
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    Default 504 tacho ?

    Quote Originally Posted by Shobbz
    Maybe its the tacho. Connected it up, out of the car and the tacho reads ~2500 on idle, and will quite happily move to 4-5000 when i touch the accelerator slightly????

    Does it need a resistor in line??? or somethign similar. Does it need to be connected to the dash via the light lead to work????

    thanks

    shobbz
    Is the 504 tacho similar in appearance etc to the 604 V6 ? If not ignore this question.
    A 6cyl tacho connected to a 4cyl will give high readings.

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