tacho strange problem

[branson]

I just bought a new faria tacho but the problem is the tacho doesnt responde.the engine is a1978 75hp evinrude 3cyl with 12 pole stator. Back of the tacho setup is position 5 for 12poles and the signal comes from the yellow-grey wire of the staror.Now with motor on idle i read ACV on signal terminal back of the tacho but nothing.Rectifier doesnt work, is this problem beacause the pulse output its before the rectifier?thanks in advance

 

[wilde1j]

Re: tacho strange problem

Rectifier probably isn't working. Check to see if you have 25 to 30 VAC across yellows to rectifier @ fast idle. If not, stator may be bad. If the stator checks ok, then carefully check all wiring associated with rectifier. If OK, the rectifier may have failed. Do diode check 1st. Also, see CDI Electronics website for more complete testing. You will need a DVA adapter.

 

[branson]

Re: tacho strange problem

Stator its ok i test it.Because the signal output is before the rectifier then it is not problem if the rectifier is bad.is this corect?

 

[Barnacle_Bill]

Re: tacho strange problem

If a diode shorts in the rectifier it will kill the input to the tach. A simple test is to check the voltage at the battery with the motor off, then check it again with the motor running. As RPMs increase you should see an increase in voltage.

 

[branson]

Re: tacho strange problem

Thank you bhile i will test it today

 

[branson]

Re: tacho strange problem

I forgot, why it is so important a good rectifier the signal output coming before rectifier