Tachometer question

[jd01]

I bought a Drag Specialties tachometer and I have a question before I go any further with the installation. I checked the search feature, but couldn't find anything on this problem. Got tach mounted to the handlebars, took tank off for wiring and accessing coil and here's what I did. Tach black wire to chassis ground, tach green wire double stacked with negative coil black wire to negative side of coil, tach blue wire and tach red wire spliced together and intend to connect this to switched wire under seat going to taillight. Well, I thought I would check to see if the tach light would work before connecting this last connection, and touched this spliced blue and red wire to the positive post on the battery. The light did come on, but the tach needle went flying all the way around past the 8000 mark and stayed there. ???
Will this correct itself when engine fires up, or is something else going on? All other connections seem ok and tight.
Thanks for any help on this.