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Thread: Holley Digital Dash Tach Issues

  1. #1

    Default Holley Digital Dash Tach Issues

    I currently have a 553-109 installed as a Stand-Alone. Using the MSD Power Grid tach output, I'm having some erratic issues. Right now the tach will jump around. Even go as high as 600K, yes 600K RPM. It seems to get worse when the headlights, turn signals or horn is activated. I've used multiple grounding sources. Power sources even going as far as running independent wires directly to battery. Still same issue. After many hours on phone with Holley, a 10K resistor was recommended. Resistor inline with tach won't work at all. Right now I'm at a loss. I don't directly think this is a Holley issue, but was hoping someone here has seen something similar and corrected. I've tried all I know to try. BTW, Digital Dash was sent back to Holley. Newest firmware installed. Tested for two days. Put it back in car same issue. MSD Power Grid gauge doesn't show the erratic spikes, just on the dash.

  2. #2
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    Dec 2009
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    Quote Originally Posted by 1fast10 View Post
    After many hours on phone with Holley, a 10K resistor was recommended. Resistor inline with tach won't work at all. Right now I'm at a loss. I don't directly think this is a Holley issue, but was hoping someone here has seen something similar and corrected.
    This reminds me of this post: https://forums.holley.com/showthread...4969#post84969
    May God's grace bless you in the Lord Jesus Christ.

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  3. #3

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    Danny, I read that post and my issues are very similar. However, a 10K resistor doesn't even allow tach signal to work. Smaller resistor values the tach will work, but problem exists still. I'm almost certain it's a car issue, just don't know what. For instance, I can unhook all headlight, parking, turn & horn wires; yet when I activate them, the tach will still act up. The horn is the worse. I can't completely disconnect steering column, and obviously the horn isn't a issue anymore, but the headlight switch still is.

  4. #4

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    1fast10, did you ever find out what the issue was, because I'm having the same problem with the tach reading? I've also tried the resistor, and it did not work.

  5. #5

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    I'm currently having the same problem. '04 Corvette ECU, +12V square wave white wire from ECU, tach jumps around at idle, off idle works fine. Sometimes it glitches when high-beam/HB indicator is on. Anybody find a solution to this problem? Also tried resistor with no success. Thanks!

  6. #6

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    Bringing this back from the dead. We have found no fix for this car. It does go away if we unhook the 1-wire alternator. Install a brand new alternator, same issues. No alternator, no problems. We even have a MSD noise filter on the main power feeding the Digital Dash & MSD Power Grid.

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