1997 Pontiac Sunfire fan

Engine Cooling problem
1997 Pontiac Sunfire 4 cyl Two Wheel Drive Automatic

i put new motor in my car and and was driving it and the engine light came on since then my cooling fan hasnt come on ive replaced the fan the gage sensor relay switch still nothing the fan does work if you un hook the gauge sensor the fan will come on plug it back in it goes off. But I noticed before I put new relay swtich in that the old one was not in right ways was turned around could this be the problem. Have new one in but nothing happens was also told to replace the temperature control sensor which I cannot find on the car or have no idea were it is. Could it be with the old relay switch in wrong way have any affect on the computer /