Ford

Only our defrosters are working no matter where you set the control. it runs off of vacuum but we cannot find the problem. can you help?

Is this a 4x4 truck with equipped with electronic shift-on-the-fly? if so, check to see if it operates. if not, most likely the vacuum pump has failed. this part is located in the engine compartment, on the passenger side, beside the starter solenoid and the heater blower motor. there is one two-wire connector connected to it, and two small vacuum hoses connected to it. the two wires are for power and ground. if both are present with the key in the "run" position, and the mode selector in any other position, other than defrost, then you need a new vacuum pump. hope this helps.