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  1. #1

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    Tach Signal Help

    I have a gen2 dash in my 93 and am struggling to get the tach to work. Initially, I was using a 96 cluster and the tach and temp gauges didn't work. It was suggested that I go to a odb1 cluster as the signal is different, so I put in a 95. Got the temp gauge to work but still don't have a tach. It does respond to rpm changes but by at least half of actual values....ie idle shows 2-300 rpm, cruising in 5th at 80 mph show 1100. I am reading that the signal from icm to tach is grouped into 91-94, then for 95 and 96-99 its a 0-5v signal that goes through the PCM. Is there anyway to alter either the signal or cluster to make them compatible? Can I swap processors in the cluster?

  2. #2
    siris's Avatar
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    They make a digital speedo tuner, will work the same for rpm. A digital controller like an Arduino can be programmed to do the same thing for probably a tenth of the price. Gonna have to take a crash course in c++ though.

    I had figured out the pulse per RPM when I was doing my boost controller, but don't remember the numbers off hand.
    72 Charger: pissed me off, on jackstands.
    95 SW1m: Dohc swap. DD. I can haz boost?

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  4. #3

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    Is the 91-94 signal a PWM style or straight pulse? I found a pwm to 0-5V converter that I'll order if it would work. Otherwise, I still need to build your ODB1 scanner. Then I can figure out a pulse:rpm ratio.

    https://www.amazon.com/Voltage-0-100.../dp/B00U7GJDVO

  5. #4
    siris's Avatar
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    PWM=pulse width modulation. Same thing

    That converter takes a pulse and makes it a variable voltage from 0-5v based on pulse width.
    72 Charger: pissed me off, on jackstands.
    95 SW1m: Dohc swap. DD. I can haz boost?

  6. #5

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    Quote Originally Posted by siris View Post
    PWM=pulse width modulation. Same thing

    That converter takes a pulse and makes it a variable voltage from 0-5v based on pulse width.
    Right, i didn't know if mine adjusted the pulse width or frequency of the pulse with rpm increases. Your wording made it sound like it could be pulse frequency. So it sounds like that converter might do it.

    Sent from my Pixel using Tapatalk

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    siris's Avatar
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    72 Charger: pissed me off, on jackstands.
    95 SW1m: Dohc swap. DD. I can haz boost?

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