Typical problems are vacuum leaks, tons of hoses all driven by a small motor behind passenger headlamp. Or a break in the shielded tach wire from the coil. Interior - check for overall condition especially leather if it has been exposed to the sun. Air bladders for seat bolsters may have leaks. Sunroof - check that it works in both modes, fully open and 'pop up at the back'.
System does have diagnostic error code capabilities through the temp display.
This is located just behind grille on the right side - long black cylinder with 3 wire electrical connector and small glass lens on top. You should see steady flow of liquid by the glass, if none or air bubbles, system is low on Freon. Body - if you live in a winter climate area with road salt or close to the ocean the body can suffer some rust. I hope this helps you out. If you need to chat let me know, take care.