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Speedo and Tach Testing?

Discussion in '"Stock" Alpine' started by Scotty, Sep 16, 2020.

  1. Scotty

    Scotty Donation Time

    Is there anything someone should know about testing for either? I have a SIV and when I drove it before the Tach worked and the Speedo was quite bouncy when I accelerated. Now they both do squat. My other instruments work, I'm figuring partly because I put in a new Voltage Stabilizer.

    I've read into the Jaeger's and it all reads like the proverbial stereo instructions to me and I'm pretty sure what I have works, just can't figure out the why.

    Any common things that pop up with these gauges that could be the culprit? Bad ground, no power, etc?

    I'm just about ready to replace both, but I know zero about these and would love insight into this from y'all and I'm not afraid to get my hands dirty learning how to fix them, that would be a cool thing to learn. Any help would be greatly appreciated! :)
  2. Tom H

    Tom H Platinum Level Sponsor

    Scotty, On the speedo, it is strictly mechanical, except the lamp, so grounding is not the problem. Most likely the cable is broken or loose.

    Regarding the tach, yes, it could be aground issue. Turn on the lights and the dash lights, if the light in the tach lights up, you have a good ground.
    Next likely issue is if the power connection to the flag terminal on the rear of the tach came loose , or broken, when you replaced the voltage stabilizer. Next likely issue is the wire looping thru the C-Clip on the rear of the tach. If you removed that loop while working on the stabilizer, you will need to put that steel C-Clip back on. See page 11 of my Tachometer article on this site: http://sunbeamalpine.org/wp-content/uploads/2017/10/alpine_tach_repair_rev5.pdf. And be sure the tips of that steel C-Clip make contact with the mating tips sticking out from inside the tach. If your Alpine has teh original wiring the white wire loops thru a plastic piece, and sometimes people just reinstall the wire and plastic piece and ignore the steel C-Clip. But that steel piece is critical to operation. The plastic peice is handy and helps the installer maintain the proper loop direction, but it has no electrical effect.

  3. hartmandm

    hartmandm Moderator Platinum Level Sponsor

    Voltage stabilizer is only relevant for the fuel and temp gauges. Not relevant for the speedo or tach.

    If you get the tach working again, if it is original, it should be inaccurate. The electrical components degrade over time and make it inaccurate. Tom H can replace the necessary components and calibrate the tach so it will be accurate again.

    If you get the speedo working again, you will probably still have a bouncy needle. There are multiple possible causes:
    1. Sharp bends in the speedo cable routing, causing binding and then releasing.
    2. Lack of lubrication inside the speedo cable.
    3. Speedometer lubrication issue.

    You can check if the issue is in the speedometer by removing the speedometer from the car, find a driver bit that fits in the speedo cable connection on the back, and then spin the driver bit (counter-clockwise for my series V, I assume series IV is the same direction) using a variable speed drill. If the needle has a bouncy behavior, then you should open up the speedo and clean it and re-lubricate it. If the needle readings seems solid, then it is probably an issue with the speedo cable routing or cable lubrication.

    A couple of Speedo rebuild articles are in the "Gauges" section at http://wp.mhartman.net/home/cars/sunbeam/alpine/info


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