so over heating when ac on find out the problem threw one of my good master tech friends so here it goes for people with the same problem and are puzzled on what it mite be ,fan clutch people one of the most notoriuos problems with termo temp fan clutches when u turn ur a/c on it produces more heat so ur fan clutch should turn on more then with ur a/c off because of the heat the condensor builds so there for over heating is caused if ur fan clutch is bad, i thought it was a blowned head gasket but how when i just put a rebuild head n new head gasket new thermostat new water pump flushed the coolant system.so thanks to my boy harmon for his tech exp and to cl fam for taking time to read this.oh ya price for fan clutch for 93 gs300 69$ from advance auto parts with my shop discount

 

What brand is the fan clutch you picked up? I'm not about to put some Taiwanese/chinese/mexican parts on my car but this is good information that I will check on mine about.

 

don't know what brand but the auto part store that i get my stuff always have reliable parts,toyota wants 175