My question is this...2007 Saturn ion won't do anything but click when turn the key. I have replaced the starter and alt tested good with a fully charged battery. What else could it be?

Check for seized up motor ( worst case scenario) could be something keeping motor from turning over like a seized up alternator , power steering pump etc any accessory driven by the serpentine belt

everything moves just fine. just won't engage starter when turn the key. it just clicks starter was replaced, alternator checked, battery checked, all good.

Did you ever fix your car? I have a 2006 ion doing the same thing the in-line fuse is good I could ark across the starter with a wrench to start it but that worked twice now nothing but clicking not the starter either I think it’s just spinning not actually engaging to start. New battery it’s got something to do with starter, ignition l, or wiring in between , I have not figured out my problem please tell me you did

Check your ground under the hood you will see a point to ground to where their are 3/4 wires going to the connection and has a nut on it just for ground.. Take the nut off of the point to ground and clean the connection with parts and brake cleaner. Wal mart has it. For about 3.00. And use clean it and reattach the wires and make sure your getting a good ground and it. Should start... You can also separate the wires and make another ground some where near the one that's their and take a wire brush that hard and course and scrub it hard and clean it with brake and parts cleaner and hook it back up and then try it.. I bet you it will start.. Mine did and every time thst happens I just clean the shit out of and reattach and it states.. Try it and let know if it works for ya..

One year ago my 07 did the same. I bought new battery new starter. I lefted it sitting for 3 months. Then I got another battery put it in n it started. A day before Xmas. A year later same thing. I'm guessing It's Electrical

So I checked my 07 with an altarmeter. It's was alternator, not my battery.. It was a short. Some were in the car something stayed on which caused a dead battery... Multameters are the best!

Yes.. found out it was my alternator. Multimeters are great to have.