[Vwdiesel] Erratic Tach

[Roger Brown]

Milt Kaplan wrote:
> I checked the nut at the added connection at fuel stop solenoid that R. Browns black box tach signal generator design uses. Its fine. The other gauges work fine at time of the tach odd behavior. Appears not be related to vibration. Also does not appear to be bad ground connection. When engine is started and running while cold everything always works fine. I'm wondering if some electronic component can become erratic after being in use, maybe from heat generated. Resistor/capacitor changing value or some solid state device inside the tach or black box can do this?     

Nothing in the electronics box really relies on any R/C values for generating the signal. 
  All it does is clean up and amplify the signal from the opto sensor and sends it on to 
the tach.  One person had trouble with the optical pickup wheel black areas not being dark 
enough.  He repainted the dark areas on the pickup wheel and it seemed to work better. 
Does the cruise control operate when the tach is jumpy?  Is the diagnostic LED on the box 
blinking normally when the tach acts up?

-- 

   Roger