***HELP tach adapter 9117 vs coyote wiring help ***

[35 Ford Hoonatruck]

Building 35 ford truck with the Coyote motor. My problem is that my Tach is not working. I purchased an additional tach adapter 9117 in hopes that I got a faulty one but they are both acting the same......I am getting NO voltage out of the Gray wire ( the one that goes to the gauge ). The way I have it wired up is I have the Red/Green wire going to my coils (purple wire) and the Red wire going to the computer. I cut the purple wire just before the harness and split it there. I have an extremely good ground of which I have moved multiple times to eliminate that.

Soooooo here is what I have.

VideoCapture_20190902-142511[1].jpg

When I turn the truck on Start and ACC (without starting the motor) I get 13.3V to the Red wire which is connected to the computer
When I start the truck ( and yes it runs which means the coils are getting voltage through the 9117 ) the voltage dips then stabilizes at 14.7volts.
then I check voltage to the Gray Wire and I have nothing.....not with the motor running or with the motor off but with ACC on.

Now for some reason I checked this......while the motor was running I disconnected the ground from the 9117 and all the sudden I got voltage to the Gray wire 13.3volts on ACC only....then 14.7volts fluxuating? I get the same voltage that the Red/Green wire is getting....almost identical.
Meanwhile even removing the ground the tach still is unresponsive.


Please tell me what I have done wrong......this gremlin is killing me.

Mahalo

Doug

[FFinisher]

There are four wires on the 9117.
Red
Red Green
Gray
Black

black is ground
Gray feeds your tach,

The red and green go in the main power feed to the coils, it must be in the main feed for the coils, not an individual coil. This is the Gray wire on the 12 pin connector near the computer. You need to cut the gray wire connect the red and green wire to the wire that goes to the coils- toward the motor, and the red wire to the end that comes from the harness-toward the rest of the vehicle.

Per my email this is how I wired it and it works on an Auto meter gauge.


You need to be sure the signal the 9117 is sending to your tach is one your tach will accept. It could be a square wave, sign wave, pulse... I have no idea what all this means(except pulse) but if it is not compatible with your tach its not going to work.

[35 Ford Hoonatruck]

Aloha FFinisher,

This is exactly how I have it wired up, instead of splitting the Gray wire in that harness, I split the purple wire that is on the other end of that harness ( the same wire changes from purple to gray at the connector ). I have red/ green going to the coils, and the red going to the computer.

Doug

[FFinisher]

Aloha FFinisher,

This is exactly how I have it wired up, instead of splitting the Gray wire in that harness, I split the purple wire that is on the other end of that harness ( the same wire changes from purple to gray at the connector ). I have red/ green going to the coils, and the red going to the computer.

Doug

Then the question is if the signal it is providing is acceptable to your tach.

Does your tach have programming instructions?

[35 Ford Hoonatruck]

OK i am such an Idiot!!!!! I had the input and output switched.....because of how the harness was sitting in the engine bay where I spliced in the wires for the 9117 the incoming and outgoing wires looked like they were going the right direction!!!!! but they were not, I had the Red and Red Green switched.....and thus no Tach signal!!!!!! But I am jumping for JOY as I have solved my last Gremlin in my electrical system and now the body can get mounted!!!!!!! HORRAY

[FF33rod]

Congrats, amazing how working through this stuff with the good folks of this forum helps see things we dont on our own. On to the next challenge....