Tach issues
 

The coil on my 86 arced to the primary side and now the tach is pinned past the red line. Car still runs like a new one. Thinking it could be either the DME driver circuit or the tach, can anyone tell me if there is a check I can do to verify the tach signal from the DME is OK? I do not have an oscilloscope, only a voltmeter. Thanks

I think that to check the signal from the ECU, you need a O Scope.

You do know someone that got a scope... Start with an A and finish with a X (4 letters) :)

My bet is on a less then a $ diode in the gauge

Thanks for the reminder JJ Can anyone tell me what kind of trace etc the DME tach output will produce? Also, if anyone knows if a multimeter can be used to verify the DME tach signal, that would be great.

Take the tach out and disconnect its signal line but keep power and GND connected. If it's still pegging you have a bad tach.

The DME puts out a square wave and you will need an o-scope to properly measure that

Thanks Ischmitz, that's exactly what I needed to know. I'll be on that this weekend.