What is the one pin sensor/(whatever it is) that is located on the top of water filler neck, my rx is an 88 gxl and it seems to be missing on mine but this car also had a small fire under the hood, I bought a new harness and this is the only plug that doesn't have a match, although I have seen some pictures of water necks that have something in them. They were listed as turbo II necks though. Any help would be appreciated on whether I need this thing or what.

 

Pick either 10 or 11.

 

i'm assuming if I have a manual trans then I don't use the one on top, only the 2 pin connector on the back of the water neck.

 

It's the temp switch for auxilialy electric fan filled to Turbos and autos. If your car doesn't have the fan then it won't have the switch.