Abstract: A fuel-saving air conditioner compressor timer is adapted for simple connection to motor vehicle air conditioner systems of the type that are manually controlled and not of the expensive climate control type. An adjustable timer may be set by the driver by means of one or more front panel controls to repeatedly cycle the vehicle's air conditioner compressor on and off in order to take advantage of the thermal time constant of the air conditioner duct system, which results in the continuing flow of cool air therefrom for a period of time after the compresor is cycled off. The on and off cycling of the compressor is adjusted by the driver so that the compressor will cycle on when the temperature of the air flowing from the duct system rises to an uncomfortable level. An optional overriding temperature control, such as a thermostat, may be provided to prevent the compressor timer from engaging the compressor until the temperature inside the vehicle reaches a predetermined level.