The ambient temp gauge is really simple. There is obviously a positive wire that goes to the gauge. Then as I remember a ground wire for the lamps inside the gauge. Then the yellow sensor wire.

The sensor is supposed to be mounted to somthing that conducts a good ground. Usually it mounts behind the airdam, which is a good place for the outside temp to be read because it is in front of the radiator.

The mount for the sensor is the (-) side, and the wire on top of the sensor is the (+). Basically keep the two isolated. I cable tied my sensor under the front bumper and used a ground wire from the mounting bracket instead, because I was having ground connection problems.

Also, make sure that it won't get snow or slush on it, wherever you choose to mount it. That will cause erratic readings when the current jumps around the sensor.