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Tachometer Schematic

Discussion in '"Stock" Alpine' started by 10sguru, Oct 4, 2015.

  1. 10sguru

    10sguru Donation Time

    I Was going through some old Alpine notes and found the attached document. It appears to be instructions on hooking up a tachometer. My OCD was wondering if anyone recognizes it and the possible source. Please advise. Thanks.


    Attached Files:

  2. RootesRacer

    RootesRacer Donation Time

    Tough to decipher the image, looks like it might show how to properly connect the stock tacho though I dont see a ground connection?

    Tom H. is the expert in such things around here.
    Last edited: Oct 4, 2015
  3. Tom H

    Tom H Platinum Level Sponsor

    From all appearances I would say this is a hand drawn, nicely done, diagram showing how to wire an Alpine electronic tach into a car that originally did not have an electronic tach. If this was included in some Alpine stuff, it seems reasonable that the author intended it to show how to install an Alpine electronic tach into an earlier Alpine that originally had a mechanical one. I note it does show the tach should get powered by +12 V, (if Neg earth car) or by ground (if Pos earth car) and shows the Case should be connected to the opposite (earth on neg earth car or -12V on a Pos earth car). This implies that the instructions are for a SV tach (Neg earth version, model 2411/01), and seems unaware of the fact that there are earlier versions of the tach designed for Pos earth cars , or that fact that either polarity tach can be converted to the other polarity internally. I would not recommend wiring a Neg earth tach, like this drawing suggests, into a Pos earth car by simply applying a ground connection to the power terminal and -12 V to the case. Too much risk of a short with the whole metal case "live" at -12 V relative to all the earth (Gnd) points around it. Not to mention the difficulty of installing the tach lamp which would cause a short unless you reversed its wiring as well.

    The drawing does seem (dotted lines just below the case) to show how to interrupt the power feed to the coil and route it thru the sense loop on the rear, but I cannot tell if the instructions are clear that the steel U-clip is needed to make the loop effectively couple the ignition pulse to the tach electronics.

    Last edited: Oct 4, 2015
  4. 10sguru

    10sguru Donation Time

    Thanks Roots Racer and Tom. I'm just getting my 1966 Ser V back on the road after a 14 year hiatus. I had misplaced my Rootes Shop Manual and just recently found it. I found this schematic folded up loose in between a couple of pages in the binder and just couldn't remember where it came from. I'm thinking it was some sort of tachometer tech article that someone wrote way back when. At any rate my OCD was getting the best of me not knowing where it came from and even why I had it, lmao. Cheers.


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