A system includes a control switch mounted in a tractor cabin and is electrically mated to a power source of the tractor. A first coolant is housed within the tractor's engine and a second coolant is housed within a trailer's heating system. The first and second coolants have unique boiling and freezing temperatures respectively. A mechanism is included for simultaneously transferring heat from the first coolant to the second coolant while maintaining the coolants isolated. The first and second coolants have first temperatures entering and second temperatures exiting the heat transferring mechanism, respectively. The first coolant second temperature is lower than the second coolant second temperature. Mechanism are included for controlling an input flow rate of the second coolant upstream from the heat transfer mechanism and for replenishing the second coolant as heat is transferred between the first and second coolants.