Now that the weather has turned warmer in NorCal I am seeing an interesting problem and need your assistance.

I have a 1993 300ce, and if the outside temp is @ 50 to 60 degrees, and the sun is shining it seems the only way to keep cool from the solar gain is to turn the temp dial all the way to max cool - as slowly turning the temp down has little to no effect on the temp of the air coming out of the outlets. I then roll it to the detent position to get full a/c from all vents at max fan speed to cool off, but when i spin the dial back to @ 65degrees it then kicks on the heater on the side and bottom vents and it gets too warm! Is the temp sensor bad, or what else would cause the temp be vlow to adapt to any temp change short of max hot or cold?

How can I stop this cycle of hot/cold/hot and spining the temp dial? In what order should I check things before I take it for service at the dealership/indie shop?

Thanks

Steve