Yamaha OX66 225 - Source of tacho signal?

[m0rt3nlund]

Hi!

I am having a problem with my OX66 225 and cannot get a tacho readout.
I have measured the green wire coming out of the ECU/CDI (The one that goes into the 10pin harness for the tachometer) against ground using AC voltage and was expecting a fluctuating reading based on the current rpm of the motor. But I have no reading at all. Tried DC too to be sure....

I have tried 3 different ECU/CDIs with same result.
I have also checked for continuity from the connector on the bottom of the ECU/CDI and throughout the 10pin harness going out of the engine and this was OK!

I have also measured the crank position sensor as I thought this could be a location for the tacho to originate, this measured a voltage that corresponded with the rpm. So figured this one was OK!

My question is: Where does the ECU/CDI get/make the tacho output signal from? Pulser coils?

Thank you, hope someone knows!

Morten Lund

 

[mjf55]

Morten, As you know, the source of the tach signal is inside the ECU. What the ECU uses to calculate and produce the signal, I don't think you will get an answer, but I hope I am wrong.
Since you have replaced / tested with 3 different ECU's, we can probably rule that out. You also check for continuity on the green wire ( tach signal ) in the 10 pin connector from the ECU to the 10 pin connector.
Did you check continuity from ECU all the way to the back of the tach?
Did you check resistance between the green tach wire and ground? Perhaps you have a shorted wire to ground.