Aftermarket Tach reads too high.

[homerj1]

Just installed one of these to my w terminal ( 1.6td)

http://www.ebay.com/itm/60MM-Stepper-Motor-DIESEL-TACHOMETER-RPM-GAUGE-METER-/220704701680?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item3363067cf0

After tweaking adjustments on the tach  it still reads 25% too high - no big deal at idle - but when 4000 rpm is really 3000.   

I installed a 47 K variable resistor ( from a mk3 3 light switch) in the w terminal line to the tach - but no real change.

Do I need a stronger\heavier variable resistor?  The local Radio Shack has only packs of resistors.

Can I steal something from another electrical device?  I was even eyeballing the pedal control on our sewing machine.   

[745 turbogreasel]

This Kit arrived With All Necessary Hardware's Including:

 
·      Gauge
·      Manual English Installation instruction

I think this says everything you need to know

but maybe a magnet trigger on the crank pulley...

[homerj1]

This Kit arrived With All Necessary Hardware's Including:

 
·      Gauge
·      Manual English Installation instruction

I think this says everything you need to know

but maybe a magnet trigger on the crank pulley...

lol,

Maybe they were just having a bad english translation day.

I know I should have spent more $$$$ or tried a gasser conversion.

But I'm still thinking a variable resistor would work -or I can hone my math skill by subtracting 25%. I do have time, as the 010 trans does all the shifting.   

[homerj1]

This Kit arrived With All Necessary Hardware's Including:

 
·      Gauge
·      Manual English Installation instruction

I think this says everything you need to know

but maybe a magnet trigger on the crank pulley...

lol,

Maybe they were just having a bad english translation day.

I know I should have spent more $$$$ or tried a gasser conversion.

But I'm still thinking a variable resistor would work -or I can hone my math skill by subtracting 25%. I do have time, as the 010 trans does all the shifting.  

Doh!!  

Variable resistor will only work in the tach - not the signal from the W terminal - as this signal is in pulses.  Damn you Kahn!!!!    http://www.youtube.com/watch?v=LTMI6v9NyJg

Here I go,    3000rpm - 25% =  2250rpm,  4000 - 25% = ........  

[745 turbogreasel]

Dakota Digital SGI 5