Printer Friendly Forum Posts - Testing Tach and VSS Wiring

Im teaching myself to fit cruise controls to cars can anyone tell me if there is a tool that i can use to find and test the vss wiring and the taco wiring . Also Where does the vss wire come from and go to i would imagin all the late model cars are the same i just have to find the the wire . I looked in list of cars in this site but the cars are diffrent to ours in australia . any info would be great thank you

The vss and tach wires can both be tested using a multimeter.

For VSS: Get the car in an open area. Set your multimeter to read AC voltage. Place your black lead to ground and the red lead to the suspect wire. Put it in drive and give it a little gas. The multimeter should read close to zero when stopped and rise to a volt or more while moving. Faster you go, higher the voltage.

For tach: Set your multimeter to read AC voltage. Place your black lead to ground and the red lead to the suspect wire. The multimeter should read close to zero with the engine off and rise to 1 - 3 volts with the engine running. Give it some gas (car in park) and the reading should increase as the rpms increase.

The VSS signal is usually found on the speed sensor on the transmission, although that usually is NOT where you tap into the wire. Assuming you have a wiring diagram for the vehicle they will list a more convenient place to pick it up at.

Tach wire is commonly found at the coil packs or the tachometer in the dash cluster. Nowadays a lot of places are recommending to go to an injector wire for a tach signal for remote starts at least. The only time I hook up tach on cruise controls is if the vehicle is a 5 speed.

Another wire some cruise controls will want hooked up is the neutral safety wire. This wire normally will see a ground in park OR neutral.

Good luck,

Mike