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timmy2 timmy2 is offline
ROW '78 911 Targa
 
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Join Date: Jul 2011
Location: Salem, OR
Posts: 10,217
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Tach movement itself or perhaps VR is going out? Any flickering of head lights?
Plug in a digital voltage gauge in the lighter socket and see if it is jumping all over while you drive to rule out the VR.
If all normal for charging volts, then maybe the tach itself is going out. If you tap the gauge does it behave normally? Mine will stick if I leave the car in the sun too long. Plastic gauge face needs a tap and all good again.

Make sure you have good continuity from purple/black at CDI 6 pin connector to the back of the gauge. (Wiggle harness around while checking)
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Dennis
Euro 1978 SC Targa, SSI's, Dansk 2/1, PMO ITBs, Electric A/C
Need a New Wiring Harness? PM or e-mail me. Search for "harnesses" in the classifieds.
Old 07-28-2017, 10:15 AM
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