Aftermarket Tach reads too high. - Upgrades (non engine related ) - VWDiesel.net The IDI, TDI, and mTDI source.

• Aftermarket Tach reads too high. by homerj1 on 21 Jul, 2013 13:10
• 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.   
• #1 by 745 turbogreasel on 21 Jul, 2013 13:30
• Quote

  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...
  
• #2 by homerj1 on 21 Jul, 2013 13:38
• Quote from: 745 turbogreasel on 21 Jul, 2013 13:30

  Quote

  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.   
• #3 by homerj1 on 21 Jul, 2013 14:17
• Quote from: homerj1 on 21 Jul, 2013 13:38

  Quote from: 745 turbogreasel on 21 Jul, 2013 13:30

  Quote

  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% = ........  
• #4 by 745 turbogreasel on 22 Jul, 2013 00:08
• Dakota Digital SGI 5