S13 SR not starting/water temp sensor reading incorrectly

[namfbroh]

Hey so I was going to work today, and on the way I noticed the coolant temp sensor in the gauge cluster jumped from normal position to really fucking hot, and then slowly crept back down, which I found weird. I went to park my car and I was idling for maybe a minute, at most, and I noticed my temp gauge go all the way to H, even though I wasn't overheating. After work, I jump into my car, turn the key, and the starter does nothing. No click, nada. I just had the starter rebuilt about 3 weeks ago so I really don't think it's the problem.

I bump started the car, got it running and as soon as it was running the gauge goes right up to H; but it wasn't overheating. I get on the road, and as I'm driving the gauge creeps back down to normal and stays that way until I get home and park, which it creeps back up to H. I find it strange that both of these problems arise at once, and I recently stopped caring and slammed my car, so I may have a rubbed harness... but assuming it's not, what could the problem be? I searched for a while and didn't get anything helpful.

It's too dark to see anything right now, but I'm just looking for some ideas.