GAUGES NOT WORKING PROPER

I have a 67 barracuda. I have a mech. oil pressure gauge in it & i just bought a new water temp. sending unit. When i started it today to see if the water temp. gauge works i noticed that both the water temp gauge & oil pressure gauge were on high. The oil pressure wire isnt hooked up. Could it be a short or a ground issue ? I realy hate wiring lol In fact the amp gauge is the only one working. As for the fuel gauge im not sure. The sending came with the car & looks like it was changed at one time. As for the ground strap i didnt have one so i made one.