In an electronic control system for a vehicle, when a switch manipulation signal is inputted from a portable radio device, a control apparatus sets a check condition for switching an air-conditioner from the present condition to a different condition as a check condition for checking a manipulation pattern. The control apparatus checks the manipulation pattern based on the switch manipulation signal and a count value of the number of switch manipulations and checks whether the manipulation pattern meets the check condition of the acceptable pattern. If the manipulation pattern meets the check condition, the control apparatus starts to turn on or off the air-conditioner.