Fan clutch? I have had very similar symptoms the last few weeks - replaced the fan clutch last night and my temp hit only 160 on the way to work this morning (normally I'll hit 190 - and I live in Denver, so it's already cool out).

 

If temps only hit 160, suspect stuck open thermostat. Or no stat.

 

Outside temp here is only 62 (Denver).

 

Should still be able to get to opening point of stat. That is one of the stat's jobs, to hold water inside the engine long enought to heat up and carry away heat to the radiator. I had no stat, ran 140-150 while 90F outside. I had a stat that moved down in the ooze of RTV (I belong to the ten gallon club) when I installed it and left a crescent moon-shaped opening that allowed some water to go by all the time, and it would stay low temp. In the 30-40F here in "winter" I'll run 178 - 183.

 

Okay SB, this just keeps getting better... Got it back from the shop again today. Said the brand new out of the box thermostat was bad & replaced it. Temp gauge is right where it should be 8:00 position on the dash with the Ultragage reading a consistent 188 degrees till I turn on the ac & it immediately jumps to the red (within seconds). Turn it off & it goes right back to the normal 8:00 position. The temp reading on the UltraGauge never climbed over 195 degrees, but the gauge on the dash sure did. And then I got a P1179 code not 2 miles from the shop. What in the heck is going on now & how does all this all come together?