1996 Buick, Battery problem and or wont turn over

I have a 1996 Buick Reagal, when it goes to start, It holds out for about 4-9 seconds, You can hear the starter trying to turn and a clicking sound. once the car starts its fine and runs good, doesnt die or stall out, once you run the car for a bit and go to turn it on again. the ignition switch doesnt turn over. It does a dead click, nothing happens. I pulled the starter out, and the alternator, both are fine. tested and chargered the battery, i ran the relays and the sensors all are fine. i cleaned the battery terms and I replaced the boths on the side post. if I go out and remove the brace remove the fuse planel remove the windshield water tank and disconnect the positive to the battery and re attacth it. it will turn over with the 4 to 9 second delay. WTF IS GOING ON, someone help please!:runaround:

How did you test the starter? Need to do a draw test on the starter, may be pulling too many amps, should be around 200amp initial draw. Did you load test the battery? It may show 12v, but fall on its face under a load. Also stated you tested the alternator, what was the output of the alternator?

This must be a connection problem or bad battery. How old is the battery? Have you checked the ground connection to the block? Follow black lead to engine block and look for corrosion. Remove the connections at battery and look very carefully at the disks in the round plastic connector. I assume a 96 has the side mounts typical to GM. You may have to pry a little with a screwdriver but behind the copper disk there may be much corrosion that is not obvious until looking close. Had this issue once... If corrosion found baking soda and water to remove deposits, spray out with WD40...