Not that I would put these gauges in my Z but since you chose to do it at least get them working right. You mentioned that nothing worked unless by the factory dimmer switch. That means you have the gauges hooked up on the wrong wire. The voltage changes on that wire. The controller that comes with the gauges is designed to have a constant 12v signal so you need to change the wire to the 12v wire activating the parklamps. The voltage stays 12v on this wire allowing gauges to work properly.
