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1976 Johnson 115hp - no tach signal

S

SaltyScot

Regular Contributor
My tach is not working on this motor. I tested signal wire continuity from the motor to the controller and to my tach and it is good. So I tried testing the output signal wire off the outboard to ground and I'm not getting any reading with the multimeter on AC or DC. I wish I had tried that before buying a new tach, which is what I'm currently trying. Both tachs are Faria Beede.

My old tach stopped working when I over-revved my old Mercury 500 in a different boat and took out either the rectifier or stator. Could connecting that presumably bad tach to this Johnson have messed up my output on this motor? What can I test further or what should I replace from here? Thanks.

Stephen
 
Well, I just pulled the rectifier off of my parts motor and tried it and it's still not working. How do I test the rectifier?
 
Those numbers mean nothing to me. I always put the digital multimeter back in the box and use the old fashioned analog one to test diodes. OR, an even more old fashioned continuity light.

There are four diodes in the rectifier. Each one must be tested separately, once in each direction. All must pass. See diagrams.
connect meter leads to one rectifier yellow lead and other to red lead. You should get either a high or low reading. Reverse meter leads. If you got a high reading before, you should get a low one now. Repeat with other yellow lead and red. Repeat with one yellow and ground (case). Repeat with other yellow lead and ground. That's eight tests. Note: If using a continuity light, results will be light/no light instead of high/low.

Rectifier 2.jpg


DIODE TEST.jpg
 
Followup---Digital multimeters cannot do the high/low test just described. That's why they have a "diode test" function. You know your meter, I don't.
 
I tested both rectifiers and they look good. So I went back to my signal wire that had good continuity. It may have good continuity, but it's not passing the signal for crap. I ran a new wire in place of the gray one and now it's working well with both my tachometers.:)
 
Grey wire may have had a short to ground. It would still have continuity, but also show continuity or leakage to ground. Just guessing from afar.
Anyhow, glad you got it fixed.
 
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