2000 Buick Regal Clicking starter

My Regal has had some coolant problems and I got them all fixed and started the car and let it run for 20 minutes then I put it back on the ramps to put the air dam back on. After shutting it off and putting the air dam back on it wouldn't start. It isn't a dead battery clicking from the starter it is a hammering clicking like the solenoid is throwing the sproket but the starter motor isn't spinning. So I took the starter off and went to a local parts store and had them bench test it and said it was good. So I went for the wiring and replaced the hot and ground wires and put new terminal ends on the cable and puyt the charger on the battery. I tried to start and still the same real loud clicking. I took the starter back off and got a new one. It does the same thing. I went through all of the troubleshooting of the wires chanking voltage and resistance with a digital multi meter and I had 12.3 volts on the battery and the starter and.5 ohms from the positive terminal on the battery to the starter and.6 ohms from the negative terminal to the starter chassis. I pulled the fan belt to turn the crankshaft a little. I turned the ignition and it started up twice. I put the air dam back on and it went back to the clicking. I tried the belt again and checked my wires again to make sure the air dam didn't affect my wires and it is all good. I am ready to give the car a stick of dynamite.