The resistance in the sending unit input to the temp.gage is getting DOWN as the car heas upyou may have to disconnect the wire from the tem. sender unit on the engine when it warm and off , turn ign on and verify that the needle at the very buttom.
The second thought is to measure the alternator voltage at 1500 rpm,making sure it not 15+ volts(sign of filing regulator or failure in stator feedbac circuit.
If the radiator core is cool while the upper hose is hot suggests bocked tubes.
If we assume the temperature sender is at a constant resistance and we lower the voltage by putting a load on the alternator, the current running through the gauge would drop, causing it to read lower. That's my line of thinking, please correct me if I missed something.
The alternator passed the testing in the charging section of the service manual. It was just under 15 volts according to my analog multi-meter. I'll check it again with a digital multimeter from a buddy though.
Here's a quick diagram of the radiator:
From what I could tell, the bottom radiator cap was a constant temperature. This rules out partially clogged coolant tubes, right?
Yesterday I flushed the radiator with the garden hose after draining it. I backflushed it by putting the hose into the lower radiator hose, then back to the top, then the lower, etc... until it ran clean.
Also, after letting the car get to the "red" on the temp gauge and dropping it down by putting an electrical load on it, I felt the lower radiator hose warm up. It seems the temp gauge is reading really high so I am stopping the motor before the thermostat opens.