Questionthankyou for guidance to previous question on this subject replaced ovp relay as fuse cap cover missing and found severe connector corrosion inside old reley did not cure my problem so checked td output from pin 1 of diagnostic socket with scope only getting flatline trace of 5 volts approx whatever rpm but tachometer still operative but tends to flicker if this td signal is weak not present is it possible that it would operate tacho but not hold in control relays or is tacho drive derived from other source pin on ignition control unit your advice much appreciated as info and knowledge hard to come by thank you
AnswerThere are two tachometer sensors.
#1. Tachometer sensor is for instrument cluster.
#2. Tachometer sensor is for OVP/engine control.
It sounds like your #2 sensor is bad.
Vehicle: 1989 Mercedes Benz 560SEC
Part: Reference Sensor
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Reference Sensor
Position
Located at front crank pulley.
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Reference Sensor
R.P.M.
http://63.89.49.212/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid...
