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Ruben

Omex 600 Tacho

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Ruben

Hello again! Today was the day of finding out how the connections of the ecu work in the tacho , after some digging i found how and where the DASH cables connect , but the question that remains is , is the original tacho from the 205 suitable for this application? I have seen somewhere here that it is possible to modify the tacho by changing the positions of the resistors or by a easier method using diodes. It got me quite a bit confused , can anyone tell me the main differences of these two methods and how can they be done! i have allready made some progress in the wiring and this shall be the one that remains to have the eletrical part done. ECU is a Omex600 aplicattion on a 205 1.6 GTI

 

 Best Regards!

 Ruben Figueira

 

 

Edited by Ruben

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petert

The easiest method is to remove/bypass the filter circuit in the tacho, if you have soldering iron skills. Then the tacho will accept a 12V square wave output from the Omex600 (12C blue/yellow).

Edited by petert
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Porter87

I did the Rev counter mod and it works a treat. Just check the fuse if it doesn’t work.... I spent a good few hours head scratching before I realised my fuse had blown

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Ruben
9 hours ago, petert said:

The easiest method is to remove/bypass the filter circuit in the tacho, if you have soldering iron skills. Then the tacho will accept a 12V square wave output from the Omex600 (12C blue/yellow).

This is what you mean?

Screenshot_20210421-171128_Chrome.jpg

Edited by Ruben

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Ruben
2 hours ago, Porter87 said:

I did the Rev counter mod and it works a treat. Just check the fuse if it doesn’t work.... I spent a good few hours head scratching before I realised my fuse had blown

How did you do it? Could you give me a explanation?

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petert

So that's my original picture (as you can see from the background), but I didn't do those mods. All I did was bridge the two pads with the line in red. Mine is probably a "dirtier" solution. It's never failed however, and given the output from the ECU is "clean", I can't see an issue with it. Maybe someone with more electronics knowledge can explain a reason? My solution is easily reversible.

205 tacho mod.jpg

Edited by petert

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Ruben
14 minutes ago, petert said:

So that's my original picture (as you can see from the background), but I didn't do those mods. All I did was bridge the two pads with the line in red. Mine is probably a "dirtier" solution. It's never failed however, and given the output from the ECU is "clean", I can't see an issue with it. Maybe someone with more electronics knowledge can explain a reason? My solution is easily reversible.

205 tacho mod.jpg

I ended up doing the solution from thw image i showed you , from what i hear from here , should work fine! The capacitor comes out as such the brown 15K resistor. And then in the place of the brown 15k resistor i welded the white one. Now its all about giving it a test! Capacitor and 15k resistor came out , i have them stored in my toolbox just in case.

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BamBamGTI

I have an Omex 500 and the same problem. Will this mod work for my ECU?

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Richie-Van-GTi
On 4/22/2021 at 10:02 AM, Porter87 said:

I did the Rev counter mod and it works a treat. Just check the fuse if it doesn’t work.... I spent a good few hours head scratching before I realised my fuse had blown

Which fuse? 

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Porter87

The reverse light and rev counter use the same fuse, it was fuse 1 on mine. I'd accidentally bridged the reverse light wires when working on the gearbox, which blew the fuse, it uses the same one for the rev counter. I spent hours tracing wires (112 for the rev counter) installing an Omex adapter all to find that I had blown the fuse.... changed the fuse and it was all sorted. 

Edited by Porter87

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Richie-Van-GTi

Thanks, i just checked with a multimeter and i have 12v on pin 1, good earth through pin 2, continuity back to the tacho driver on pin 3, cannot find what pin 4 goes to (wire 112b), i assume that went to the old ecu or tachy relay. Haynes doesnt show it. Still cannot get mine to work. 

Edited by Richie-Van-GTi

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