Tach Question for 79 115 Johnson

[Alpinegold]

If it ain't one thing it is another. I don't know anything about the tach but it stops at 1500 rpm when the motor is off. It does move when I running. What do I need to do first to see if the tach is any good. It is the orginal that came with a 78 V178 Ranger. The motor is a 79. The motor runs great.

 

[HighTrim]

Re: Tach Question for 79 115 Johnson

What is the rotary dial set to on the rear of the tach?



Tachs read off the alternating pulses from the stator. Any of the leads from the stator charging portion can be used for the signal. The designated tach signal wire is merely attached to one of those. Tachs have rotary switches on the back that set it to different numbers of coils in the charging circuit, times two because there is a positive and negative pulse for each coil for each cycle. Tachs measure pulses. That being said, you need a tach that has the setting that you need designated on the rotary switch, and set accordingly.

 

[ezeke]

Re: Tach Question for 79 115 Johnson

Most tachometers read the RPM that was showing when the ignition switch was turned to OFF. So if you were running at 1500 RPM and immediately turned the key to off, it would show 1500 until you turned to RUN again when it would default to zero until the engine was cranking again.

If the gauge shows zero when you first turn the key to run, it is normal.

If the tachometer does not change at all, check the sender wire [grey] first, then the rectifier, then the tachometer.

 

[Alpinegold]

Re: Tach Question for 79 115 Johnson

I am at work right now but when I get home I will check the back of the tach and post what I find. Thank you very much for your help.

 

[HighTrim]

Re: Tach Question for 79 115 Johnson

Excuse my response and refer to Ezeke's, misread your post. Good luck.