Tach Going Bad???
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Tach Going Bad???

  1. #1
    Super Moderator HammerDown's Avatar
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    Question Tach Going Bad???

    All of a sudden when running at RPM's the tach will die.
    Shut the engine off-fire up the engine and the tach comes to life again and may be fine for several miles.
    All wiring appears to be solid > tach dieing a slow death?

    Over the years this is the second VDO gauge to do this.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Pro Gas Jet RedPearl's Avatar
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    Default autometer

    i had a 10 year old autometer tach go bad sent it back to autometer and they replaced it for nothing. great service.
    Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic!

  4. #3
    Cas
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    I had a nut come loose (no comments please) inside a VDO on my first boat back in 1979. Every time the tach hit 1800 rpms, the engine would shut off...restart, hit 1800, dies. What a pain in the arse to find that one!

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  6. #4
    the padawan
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    sounds like you have a bad ground/lead wire maybe,

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    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by Bangingears View Post
    sounds like you have a bad ground/lead wire maybe,
    If so, it must be inside the tach > everything outside is solid.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Senior Member DuaneHTP's Avatar
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    Disconnect the wiring in your boat and hook it up with jumper wires. Battery, Ground, Tach Signal. Run it that way and see if there's any difference. If that cures it, it's in the wiring, a bleed through from something else, or ground problem. If not; it's probably the tach..
    Duane HTP
    Last edited by DuaneHTP; 07-28-2010 at 06:23 PM.

  9. #7
    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by DuaneHTP View Post
    Disconnect the wiring in your boat and hook it up with jumper wires. Battery, Ground, Tach Signal. Run it that way and see if there's any difference. If that cures it, it's in the wiring, a bleed through from something else, or ground problem. If not; it's probably the tach..
    Duane HTP
    Disconnect the the wires from behind my tach...and run 3 jumpers from the junction block > behind the engine and up to the dash > them be some long ars jumper wires
    But I'll give it a try
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

  10. #8
    Super Moderator HammerDown's Avatar
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    Exclamation

    UPDATE...
    It appears one or two of the male-connections is loose at the back of the Tach.
    I took apart my prior VDO tach and inside there are 3 delicate solder joints that can easily break (if) the wires going to the back of the instruments have movement from vibrations/bounding in the chop.
    I fully secured the wiring harness to eliminate ANY movement.
    Hope that's the easy fix > crossing fingers
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Super Moderator HammerDown's Avatar
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    Thumbs up

    UPDATE -2
    I got inside the gauge, it appeared the 'inside' ground prong was not making a good contact.
    A trailer test shows all seems to be working fine again > testing on the water Friday. (fingers crossed)
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

  12. #10
    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by DuaneHTP View Post
    Disconnect the wiring in your boat and hook it up with jumper wires. Battery, Ground, Tach Signal. Run it that way and see if there's any difference. If that cures it, it's in the wiring, a bleed through from something else, or ground problem. If not; it's probably the tach..
    Duane HTP
    Digging deeper, just got the engine running from winter hibernation and VDO tach is dead.
    I just did/test a dedicated ground wire from tach to neg battery terminal, still dead.
    Next, I'll try a dedicated wire to the coil and battery +

    I think the VDO is junk but I'll experiment in my back yard anyhow.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

  13. #11
    Cas
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    Quote Originally Posted by HammerDown View Post
    I think the VDO is junk but I'll experiment in my back yard anyhow.
    I found an awesome tool that fixes bad tachs real quickly and efficiently
    Name:  pACE3-956550reg.jpg
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  14. #12
    Senior Member bp298's Avatar
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    junk the thing and go auto-meter. you won't regret it. they work great, and if there's a problem, they have great tech support....

  15. #13
    Senior Member YumaJet's Avatar
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    Quote Originally Posted by HammerDown View Post
    Digging deeper, just got the engine running from winter hibernation and VDO tach is dead.
    I just did/test a dedicated ground wire from tach to neg battery terminal, still dead.
    Next, I'll try a dedicated wire to the coil and battery +

    I think the VDO is junk but I'll experiment in my back yard anyhow.

    with all your hard work and time, you could've ordered a new one and been crusing in style with a autometer. in a boat, if it doesn't work, toss it and get a new one.
    boatless....

  16. #14
    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by YumaJet View Post
    with all your hard work and time, you could've ordered a new one and been crusing in style with a autometer. in a boat, if it doesn't work, toss it and get a new one.
    I'll let the next owner worry about a new Autometer tach...I just wanted to run some dedicated wires to confirm either my VDO was bad or, there was infact a wiring issue(very doubtful)my wiring is bad.
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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