Why is my car not starting? It turns over but doesn't crank.. What could it be?

No by turning over I mean that the ignitition hole that I stick my key in turns, I hear NOTHING. That's what I meant by crank. My lights in the car turn on, the battery is fine, nothing is dim, and I can roll my windows up and down with the radio on. Yes, when I turn my key, every light on the dash lights up, but once it clears, the only light that remains is the service engin light. There is no clicking. The alternator is fine, I'm assuming that my starter is being disabled some how or another. Initially, I thought it may have been my battery because I did find that the ground connection was loose. Tightened that up. It's not loose any more, but I am still having issues. It cleared up after a few days, but started doing it again. Took it to the mechecanic. They thought it was the ground terminal.. But they replaced that. And nope. Wasn't the problem because now it's doing it again. My dash does not give ANY other clues of what it could be. And yes I have tried the spare key. Same thing. Sometimes it works. Sometimes it doesn't.

ok,then you have a NO CRANK/NO START CONDITION THEN..i assume you have tried the spare key(s) also? there are problems with the two wires on the ignition/key switch and your security system does disable the starter/injectors/coils.is the chip on the key worn down that you can tell? it must have the correct resistance for the car to start.the security system gives lots of problems on this car.i read about one guy going to radio shack and buying some cheap resistors and soldering them into the security system and no more problems for him.some go to the DEALER?? and pay $$$$$$$ and still not fixed.

Well I don't think it's my key, because I have tried the spare and it does it sometimes and sometimes it doesn't. It's like my car has a mind of its own. Lol especially at the wrong moments. I think your right. I think it's the two wires. Gotta figure out how to get to them. Lol. My keys appear to be fine. It makes perfect sense that the wires may be loose or whatever and that that could be the reason behind all this. But ya. It's real frustrating. Thank you for your help! :)

Gotta be careful when you do that!! any YELLOW coated wire in there has something to do with the AIRBAG! disconnect the negative battery cable or both if you want, at least 15-20 before touching anything so the airbag will bleed off.go to youtube and put this in the search bar>how to replace the key cylinder on 1999 Cadillac Eldorado<there are several videos on this.i believe the 3rd one down is yours or most GM's....you will have to go to the ZONE and rent a couple tools to do this>>good luck!

Lol will do! I would hate for the airbag to deploy as I am trying to do that. Lol omg. Ok thanks again. I will go on YouTube and look it up. :-D

10-4.post findings/results.