Tachometer wiring

[balboabob]

Hi, I have just picked up a tach for my 1985 40hp 2 stroke. (see attached photos). I Located the connection points on my control harness. I am confused as to where the yellow (+ power) wire will connect to my tach as it was the only wire not connected when I got it. Can anyone help?
Thanks, Bob

 

[mjf55]

What brand is the tach? Should be listed on the front. Post a picture of the front of the tach.
Are there any markings on the back by the wires? I dont see in the pictures.

 

[Silvertip]

Tachometer marking for +12 volt connection is "I" (ignition).

 

[balboabob]

No Title

What brand is the tach? Should be listed on the front. Post a picture of the front of the tach.
Are there any markings on the back by the wires? I dont see in the pictures.

Here is a picture of the yamaha tack, it is from the 80-90 period. I have room on my control box harness for the 3 black green and yellow wires seen in pics 2,3 and 4. however the onter end of the yellow wire (fused) needs to plug somewhere??? see pic below

 

[balboabob]

Tachometer marking for +12 volt connection is "I" (ignition).

where should I plug in the other end of the yellow wire?

 

[Silvertip]

As I explained, the "I" terminal on the tach gets +12 volts. If there is a fuse in the yellow wire, it is the power source so it goes to the "I" terminal. If there are no markings on the tach then you need to do a process of elimination. The Tach has an internal light, an\ "S" (send/signal) which comes from the stator on the engine, a ground, and the +12 volt "I" connection. Keep in mind some of the very old tachs did not have or need a +12 volt connection but I doubt yours falls into that category.

 

[mjf55]

Looks to me, based on the first photo, there appears to be an open terminal. The double black wire on the right side looks like it goes tonthe top terminal. Hard to tell for sure because of the boot in between the two terminals. If I an correct that the double black wire only goes to the top terminal, then the bottom one is open and should be for the yellow wire.

 

[balboabob]

Looks to me, based on the first photo, there appears to be an open terminal. The double black wire on the right side looks like it goes tonthe top terminal. Hard to tell for sure because of the boot in between the two terminals. If I an correct that the double black wire only goes to the top terminal, then the bottom one is open and should be for the yellow wire.

CPO, ok you might be right, the booted double black are connected to a center terminal which is bridged to the top terminal, and Yes the bottom terminal is open. I guess I will connect the yellow wire there and see what happens.
My concern was that all the other wires were connected when i got the guage, and I thought maybe that the yellow wire had to go to the positive battery terminal.

I will see what happens this weekend.

 

[mjf55]

The yellow wire is for +12 volts to the tach. Somewhere it connects to battery voltage.
Just to recap the wire colors in case you need it:
The Blue and black pair go to the bulb in the tach. Black is ground. Blue connects to the other bulbs in the instrument panel.
The double black is ground.
The green is the tach signal
The the yellow is the +12 volts, turned on when the ignition is on. That is why it is sometimes marked "I", as SilverTip explained.

Will the one of the yellow female plugs fit over the terminal?