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Problems installing tacho

Discussion in 'VT - VX Holden Commodore (1997 - 2002)' started by Cannman07, Jan 17, 2020.

  1. Cannman07

    Cannman07 New Member

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    Thanks mate, I'll grab one from somewhere and hook it up.
     
  2. Cannman07

    Cannman07 New Member

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    Where would I get one of those resistors?
     
  3. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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  4. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    This is the colour code for 10k 1/4 watt, [​IMG]
     
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  5. ltdslip

    ltdslip Member

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  6. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    It says to use 10k .25watt I don't know if going double will cause a issue, your choice I know what I would do spend the 9 and get the right one as the installation tells you. Or try ebay or the web and get one cheaper if your not in a hurry.. Go to a tv repair joint they will have some or even a computer repair shop.
     
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  7. ltdslip

    ltdslip Member

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    Whats known as a pull-up resistor, It needs to be 10kohm for sure but as far as the wattage rating there's little heat going to be dissipated by the resistor,
    so 1/4w or 1/2w it wont be a issue.
    Search for 5v to 12v pull-up resistors or tacho pull-up resistors
     
    Last edited: Jan 19, 2020
  8. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    Yeah I thought so, but wasn't game to say just in case something went wrong, cheers.
     
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  9. Cannman07

    Cannman07 New Member

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    Thanks for all the help, I'll go buy one tomorrow
     
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  10. Cannman07

    Cannman07 New Member

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    Update on my tacho problem
    After getting a 10k .5 watt resistor and hooking it up it made no difference so I emailed the SAAS tech support and after telling them all of the above they asked me to send the unit back so they could test it. It tested fine but they sent me a new one in case the other had an intermittent fault. Installed the new one with the same result as before so emailed them again and they said it has to be weak rpm signal as the smaller tacho works and the big tacho has power, they told me to I install a 1k .5 watt resistor but this didn't work either. I'm not sure what to do now as I've tried all suggestions. Any ideas at all would be appreciated.
     
  11. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    Are you putting it on the correct way? Bridging + power to the tacho wire with the resistor.
    We know its weaker hence the reason to boost the volts, Commodore run on 5v if you bridge +12v power across to the tacho wire with the resistor it will add the extra volts to get it to run.
     
  12. Cannman07

    Cannman07 New Member

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    Yep, I'm bridging it between the red and green wires which are 12v and tacho wire.
     
  13. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    Well I'm stumped then, maybe have a Auto elec to have a look.
     
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  14. ant797

    ant797 Active Member

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    Get your money back buy a different tacho
     
  15. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    Only other thing I can think of is the resistor isn't correct you might need a wire wound resistor not a carbon or metal film one.
    Or your not wiring it right to suit your new configuration on the big tacho plug. I'm not saying your not.. Just find it odd that the little one working and the bigger one wont.. One like this but they don't come in 10k @ .5 W. at jaycar

    https://www.jaycar.com.au/1k-ohm-5-watt-wire-wound-resistor/p/RR3298
     
  16. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    Which are you using, carbon or metal film? Metal foil be the one you want.
     
  17. Cannman07

    Cannman07 New Member

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    I'm not sure which they are, I bought them from an electronics store. They're just a standard resistor.
     
  18. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    Ok done a bit more reading and found out this at idle 800-1000 rpm = about 1.6v on your tacho wire, so you will need to work out all contact the manufacture, you will need to add about 10.5v to the tacho wire to make it move.
    But I think you will need a inline diode to stop the power you add feeding back to your computer . I think just stick with the old one or take it to a auto elec.
     
    Last edited: Feb 15, 2020
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  19. the_boozer

    the_boozer no more VK

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  20. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    That resistor says 4cyl, what op needs is to boost the signal right on or the rpm will give a false reading, Best thing to do is at idle test the volts from the tacho wire to make up the different to get 12v.

    If it reads say 1.4v then you will need to add a resistor from the 12v source that will drop it to 10.6v, but u will need to cap off the feed wire from the computer or risk damage, u can do that by adding a no resistance diode. His a rough diagram.
     

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