The HV-101 Heavy Vehicle HVAC System is based on a Freightliner Business Class M2 commercial truck and has been specifically designed for the instruction of air conditioning systems used in heavy duty vehicles. The trainer is designed and constructed using brand new OEM components and has been engineered with respect to OEM design and function. The trainer is equipped with an electrical break out box providing easily accessible electrical test points for the HVAC control head. Clear sight glasses have been installed in the high side (liquid) and low side (suction vapor) lines at the H-Block TXV that allow students to observe the changes of state of the refrigerant.