what causes car to run hot when ac is on
07-19-2006, 10:11 PM. Also contributing to it is your A/C's condensor, the radiator-like (actually, it is essentially a radiator) thing that sits in front of your car's radiator. When you run your A/C the condensor gets hot too and must be cooled off via air flow in addition to the cooling system's radiator.he engine is working to turn the pulley to drive the compressor and the load is not inconsiderable.Also contributing to it is your A/C's condensor, the radiator-like (actually, it is essentially a radiator) thing that sits in front of your car's radiator.