If a scope is not available, you can use a DVM in the AC volts setting to read the voltage. If you rev the engine and you see a proportional increase in voltage to RPM, it is likely the tach pickup coil is good. If you get no voltage then it is toast.
Quote:
Originally Posted by techguy512
Using a constant current source, put 30 to 50mA through the pickup coil (pins 7 and 9 in the amp socket). With the scope on AC coupling, you should get a zero volt signal when measuring from pin 7 (gnd) to pin 9. When the engine is started, you should see a small 'blip' once per crank rev.
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