[msinc]

I hate to post an answer that I see all the time anyone asks an electrical question...it is so often repeated that I feel like these people just say it to look like they are experts but in reality are clueless, but here goes.....since you say both the sensor and the dash switch don't work it makes me think of a ground problem. The all to often repeated and so conveniently replied all purpose "check the ground".....but in this case, it might actually be the problem. I own a Superformance with an all aluminum 427 stroked to 458. It will heat up a little if I am idling in traffic in the heat of the summer. I believe this is normal and I have to "head it off at the pass" by hitting the overide switch on the dash if it looks like I an coming up on a traffic sit scenario. If I wait until I am sitting there and the temp starts to elevate it will stay elevated even with the fans running. Now, understand that "elevated" and overheating is two different things. I don't think it hurts it to run a little elevated, but I don't like it and I hit the switch, again, before I get into the situation of sitting for a while.

Edit: the problem I have had is if I go for a ride and it is at full operating temperature and then I park it for a while, especially in the hot sun. It does not want to start and cranks over for a while {as opposed to an immediate start up like when it's cold}. I know you cant always do this, but if I let the fans run and open the hood after shut down for a few minutes to cool things down under the hood it is fine.