I've got my autometer tach wired up to a keyed ignition with 4 amp fuse, 14 gauge into a 18 gauge running to each dash gauge. 18 gauge neg merging into a 14 gauge going to chassis ground. when i turn on the ignition everything lights up fine, gauges come on, wide band turns on. But when I press the test button to see what rpm my shift light is set at, everything goes dim, and the wideband flickers. I haven't put a multimeter on it yet (one of the hire hands have it missplaced someplace in the shop) but to me it seems like a drop in voltage which seems strange. I talked to auto meter about it, i had ground going to the battery before and they advised me to go to chassis ground but it made no difference, thoughts?