I would like to know how to hook up a 2 1/16" Isspro Tach to my 92 Dodge Ram Diesel. I am trying to hook it into the factory tach plug under the dash. The tach has 5 wires coming out of the back of it. 2 for the light and 3 for the controlling the gauge. The 3 are white, red, and black. So far I can't get it to work. Not sure which wires plug in where. Thanks.

 

Let me see if I remember correctly.

1st, do you have the ISSPRO wiring harness that has the little filter thingie in it? If you have flat faced tach, you will likely need it.

Truck side-
Orange is dimmer light
Grey is signal wire
Black (b/t orange and grey) is 12v ign hot (FSM calls it red(?))
Other Black is ground

Gauge side-
White- signal (may also use yellow from ISSPRO harness)
Red- 12v
Black- ground
Green- goes to the light.
Tie the light and gauge grounds together

Daniel

 

Okay, I have the Isspro wiring harness. Do you know why there is a yellow wire too since there are only four wires coming out of the end? I checked my plug w/o motor running and got 4.5 volts out of the signal prong and 10 volts out of the ignition hot wire. When motor running, the signal wire is showing 4.5 constant volts while the other jumped to 14 volts. Shouldn't the signal wire be pulsing when the engine is running? Thanks for the response. Kevin

 

The yellow wire is the alternate signal wire, to use if you have an EV series tach. So, you use EITHER the white OR the yellow.

DP

 

Okay thank you. I think I might have tried hooking it up that way and nothing changed, but I can try it again. The neibor has an older Dodge like mine. I might try checking his plug and seeing what I get with the motor running.