1994 Mustang

Section 12-00: Climate Control System—Service

1994 Mustang Workshop Manual

DIAGNOSIS AND TESTING

Symptom Chart

Condition	Possible Source	Action
Vent Does Not Operate Vent Always On Insufficient Vent Operation	No vacuum to control assembly. Damaged vacuum control motor . Damaged/kinked vacuum hose.	Go to Pinpoint Test A.
Heat Does Not Operate Heat Always On Insufficient Heat	No vacuum to control assembly. Damaged vacuum control motor . Damaged/kinked vacuum hose. Damaged/plugged heater core .	Go to Pinpoint Test B.
Defrost Does Not Operate Defrost Always On Insufficient Defrost	No vacuum to control assembly. Damaged vacuum control motor . Damaged/kinked vacuum hose. Damaged/plugged heater core .	Go to Pinpoint Test C.
A/C Inoperable A/C Always On	Blown fuse. Circuitry short/open. A/C relay damaged. A/C system discharged. Switch damaged.	Go to Pinpoint Test D.
A/C Operates Improperly	A/C cyclic switch damaged. A/C refrigerant system leaks.	Go to Pinpoint Test Step D11.
A/C Always On	Damaged A/C heater switch. Damaged Constant Controlled Relay Module (CCRM).	Go to Pinpoint Test Step D13.
Heater Blower Motor Does Not Operate	Blown fuse. Circuitry open/shorted. Blower motor switch damaged. Transfer housing to case bolt damaged. Heater blower motor.	Go to Pinpoint Test E.
Heater Blower Motor Runs Constantly	Heater blower motor switch resistor. Blower motor switch .	Go to Pinpoint Test Step E13.
Heater Blower Motor Does Not Operate Properly	Heater blower motor switch resistor. Blower motor switch .	Go to Pinpoint Test Step E13.
No Switching In Operation between Fresh Air and Recirculated Air	No vacuum to control assembly. Damaged vacuum control motor . Damaged/kinked vacuum hose. Damaged function control switch.	Go to Pinpoint Test A.
Noise While Operating Climate Control System	A/C compressor. A/C clutch. Damaged drive belt .	Go to A/C Compressor or A/C Clutch in Description and Operation.
Noise While Not Operating Climate Control System	A/C clutch. Damaged drive belt .	Go to A/C Clutch Description and Operation.
Engine Cooling Fan Does Not Operate When A/C is Activated	Constant control relay module damaged. Circuitry damaged. Cooling fan motor damaged.	Go to Pinpoint Test F.