tach reading wrong

[rob 135]

73 135 Johnson , What should AC voltage be on gray tach wire? Or what would HZ be? Tach only goes to 3 grand but idle rpm is ok . Tried another tach same thing. Is charging and rectifier test ok Tach is set to 12 poles . Any ideas?

 

[Joe Reeves]

What tachometer do you have? Were both tachometers you tried identical? Is there a dial on the back of the tachometers where one can set it #6, the #6 indicating "pulses"? Or, does the tachometer simply have terminals? Can you insert a picture of the back of the tachometers?

I've been in this line or work and have never looked into the actual AC or HZ readings.

 

[boobie]

Set the tack on 6 P and see what happens.

 

[rob 135]

Two different brand tachs . Back of tach says poles,12 , 10 , 6 ,and 4 poles

 

[gm280]

Two different brand tachs . Back of tach says poles,12 , 10 , 6 ,and 4 poles

Are those different places you can connect the signal wire too or are they aside of a selector switch? If it is a selector switch setting, switch it back and forth a few times to clean the internal contacts and make a better connection. They can get dirty some times.

 

[Joe Reeves]

Does it actually say "Poles" on the back of that tachometer... or is it a dial and simply says "P"?

If "P", it's referring to "Pulses". That engine emits six pulses from the charging system which operates the tachometer... set it to #6.