itchy5

hi guys, first time posting here.

I recently purchased and installed a sunpro tach III on my 95 sentra XE and after i wired it to the ECM's blue wire (tach sensor) i turned on the engine and the RPM went to 4500 and stayed there. If i reved the engine sometimes it would drop to 2000 RPM for a second but always went back to 4500 untill i turned the motor off. I wired the dimmer, ground and power wires to my rear window defroster button on my instrument panel. Could a bad ground be the problem?

any help would be much appreciated thanks

EDIT: i tried the blue/orange wire, which is what i read was the tach sensor for the B14s on the tach write-up and i got nothing, it stayed at 0 RPM... i also heard the WHITE/BLACK At Pin #1 Can Also Be Used For Tach Signal. on the12volt.com, should i give that wire a try?

EDIT#2: the white/black wire got it.