I have a 69 SS that did not originally come with the tach gauge cluster. Any car should be the same. I will be putting one in this spring. Currently, I have an aftermarket gauge package with the amp, oil, and temp gauges. Currently, the amp guage is in series with a red wire that comes from the battery/alternator area and the other end goes to the battery terminal on the horn relay (right side screw). I know this is not correct because if my amp blows, I lose my hot or switch power. I have seen diagrams that show where to connect an amp gauge and have also been told by an "expert" that all I have to do is connect the amp gauge from the junction block on the radiator support to the horn relay. Basically, just run a new wire in parallel with the existing, red wire. Is this correct? Second, when I open my door or run the car whether at idle or driving, the amp shows just slightly negative and if I turn the lights on, it goes more negative. Is this correct or should it go positive at some point? If I had a higher output alternator, would it go positive? I thought that it should measure output current because it is connected in series with the alternator before any load. From the end of the wire connected to the horn relay, I have continuity to the back wire on the alternator and the wire going to the junction block to the battery. All wires were disconnected during the continuity test. Any help would be appreciated. Thanks.