Got a couple of these Megan Temp Gauges, H2O and Oil… I misplaced the boxes and was wondering if anyone has a quick Link or off the top of there head can tell me what the 4 Colored wires are mean…
From What i remember…
Blue - ?
Red - Power?
Black - Ground?
Purple - ?
Thanks
Red is Power, Black is Ground, Purple is your signal wire and blue I don’t remember using. I had my guages (in my old 240) wired to the headlights using the red wire so when I turned those on, the gauges lit up too.
I hope that helps out a little. 
Blue has something to do with the Dimmer Switch or ON/Off sWitch
^^^^
Oh yeah that was it. Well like I said, if you wire them to your headlights you don’t need to use the blue wire. I had Megan’s in my car and you can see them just fine during the day and they actually dim for night use when I turned on my headlights.
here’s what is says right on the box… just to make sure… red is +12v, black is ground, blue goes to temp sensor, and purple is the dimmer