Abstract: A presettable fuel-flow monitor and automatic air compressor cut-off for a motor vehicle alerts the driver to inefficient vehicle operation, and during such operation, cuts off the air conditioner. A Bourdon tube is operatively connected to engine vacuum and is adapted to move in response thereto. A switch contact, adapted to be activated on a given displacement of the Bourdon tube, is positioned a preset distance from the Bourdon tube. A secondary switch, in series circuit with the air conditioner switch, is normally closed and applies electrical power to the magnetic clutch for air conditioner operation. An alarm or signal, consisting of either a light, or audible means, or both, is connected to electrical power through the switch contact. When changes in engine vacuum cause the Bourdon tube to move a preset distance, the tube operates the secondary switch opening same thus cutting off the air compressor. Thereafter, the tube engages the switch contact to apply power to the alarm.