I was checking my tach circuit the other night by injecting a signal into the amplifier and bypassing the tach pickup to get the tach to read somethingeek: . As I increased the signal (Hertz), of course the tach did not work , but I heard the shutdown solenoid kicking in and out. Do these engines have rev limiters? I also obtained a schematic of the circuit from M.B and it shows a wire going to the overload protection control unit. Is this a rev limiter? If it is my circuit appears to be working, but my tach is not. FYI If you want to check the tach pickup, I measured it with an ohmmeter and found the outsdie, or yellow and black wires should read about 70 ohms. The center pin appears to be a shield.


PeterG

79 300SD 75K miles