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Discussion in 'VT - VX Holden Commodore (1997 - 2002)' started by Cannman07, Jan 17, 2020.
Thanks mate, I'll grab one from somewhere and hook it up.
Where would I get one of those resistors?
Go to jaycar and see if they have one single if not they have a pack with different sorts that does for 8.99, only one I can find listed as single is 10k 0.5 but you need a 0.25 / 1/4 watt.
This is the colour code for 10k 1/4 watt,
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.
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
Yeah I thought so, but wasn't game to say just in case something went wrong, cheers.
Thanks for all the help, I'll go buy one tomorrow
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.
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.
Yep, I'm bridging it between the red and green wires which are 12v and tacho wire.
Well I'm stumped then, maybe have a Auto elec to have a look.
Get your money back buy a different tacho
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
Which are you using, carbon or metal film? Metal foil be the one you want.
I'm not sure which they are, I bought them from an electronics store. They're just a standard resistor.
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.
https://www.enginemaster.com.au/classic-instruments-cisn10k-pull-up-resistors-tach hows the price of this one wonder if anyone has ever brought 1 lol.
try reducing the value of the resistor 8k ,5k ,3k,1k .I wonder if trev is onto it with the voltage going back to the pmc causing the problem not that I have encounter that before but I only follow diagrams Im not a ginger beer .
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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