VSS wire
 

Hey folks, honestly never had to deal with HU that needed a wire tied into the VSS, im just wondering a little bit about it, to the best of my understanding it tests as AC when vehicle is running, does it meter similar to a tach wire? what kinda of voltage am i looking for, is that the proper testing procedure? thanks for any help

have you never isntalled a nav unit before???

Vss is not necessary for nav to work properly. Many cars do not even have vss. To test, put meter on ac, probe wire and roll car back and forth, look for reading to fluctuate.