I've had summit electric gauges in my truck for well over a year now. I can not get a constant reading out of them, or atleast a reading that I can trust. I made a quick video to show what they do. Please take a look and let me know if you have any advice.
BTW the gauges are wired into an aftermarket fuse panel for constant 12V power, and a relay block to power the ignition on. The flood lights are wired into the same aftermarket fuse panel, but the fan is not.