[Vwdiesel] Tach signal box

Dave Heart teacher525 at hotmail.com
Sat Jun 2 16:48:48 EDT 2007

When erratic the cruise stops working as well also in the black box
the led lights but doesn't seem like its flashing then.. Im bouncing
the sensor off the inside side of the sprocket using metal tape
sections instead of using the painted wheel but can't see why
everything always works fine everytime untill engine warms up! Most
of my trips are short so no problem until I go for a longer drives.

>>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
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>>Vwdiesel at vwfans.com
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