Symptom Chart - Climate Control Systems

WARNING: This page is about a different car, the 2010 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Some PCM DTCs may inhibit A/C operation. If any PCM DTCs are retrieved, diagnose those first. Refer to INTRODUCTION - GASOLINE MODELS .

SYMPTOM CHART - CLIMATE CONTROL SYSTEMS

Condition	Possible Sources	Action
No communication with the HVAC module	Fuse(s) Circuitry open HVAC module communication network	REFER to MODULE COMMUNICATIONS NETWORK .
Unable to duplicate the customer concern and no DTCs present	HVAC system and/or related components	GO to PINPOINT TEST I .
Incorrect/erratic function in AUTO mode	Circuitry open/shorted In-vehicle temperature sensor HVAC module	GO to PINPOINT TEST S .
Reduced outlet airflow	Circuitry short A/C compressor clutch air gap A/C pressure transducer A/C clutch relay Blower motor Blower motor control PCM	If the A/C compressor does not cycle, GO to PINPOINT TEST N . If the A/C compressor cycles normally, GO to PINPOINT TEST R .
The air inlet door is inoperative	Circuitry open/shorted Door actuator Air inlet door binding or stuck HVAC module	GO to PINPOINT TEST J .
Incorrect/erratic direction of airflow from outlets	Circuitry open/shorted Door actuator Mode door(s) binding or stuck HVAC module	GO to PINPOINT TEST K .
Insufficient, erratic or no heat	Low engine coolant level Engine overheating Plugged or partially plugged heater core Temperature blend door is binding or stuck Temperature blend door actuator Heater hose is kinked or binding	GO to PINPOINT TEST L .
The air conditioning (A/C) is inoperative	Fuse(s) Circuitry open A/C system discharged/low charge PCM HVAC module A/C clutch relay A/C compressor clutch air gap A/C pressure transducer Evaporator discharge air temperature sensor A/C clutch field coil	GO to PINPOINT TEST M .
The air conditioning (A/C) is always on - A/C compressor does not cycle	Circuitry shorted PCM A/C clutch relay A/C compressor clutch air gap A/C pressure transducer A/C clutch field coil Evaporator discharge air temperature sensor	GO to PINPOINT TEST N .
The air conditioning (A/C) is always on - A/C mode always commanded ON	Circuitry shorted PCM HVAC module	GO to PINPOINT TEST O .
Temperature control is inoperative/does not operate correctly	Circuitry open/shorted HVAC module Temperature blend door is binding or stuck Temperature blend door actuator	GO to PINPOINT TEST P .
The blower motor is inoperative	Fuse(s) Circuitry short/open Blower motor relay Blower motor HVAC module Blower motor speed control	GO to PINPOINT TEST Q .
The blower motor does not operate correctly	Circuitry open/shorted Blower motor speed control HVAC module	GO to PINPOINT TEST R .
The temperature set point does not repeat after turning the ignition switch OFF	Fuse Circuitry short/open HVAC module	INSTALL a new HVAC module. REFER to CLIMATE CONTROL .
Inaccurate external temperature display	HVAC module Ambient temperature sensor	REFER to description and operation of the HVAC module external temperature display. If the external temperature display is not operating as described and no DTC is present, CARRY OUT the Ambient Temperature Sensor component test. If the sensor tests OK, INSTALL a new HVAC module. REFER to CLIMATE CONTROL . TEST the system for normal operation.
A/C pressure relief valve discharging	High system pressure A/C pressure relief valve	CHECK the high side system pressure. If the pressure is below the A/C pressure relief valve open pressure, REPLACE the A/C pressure relief valve. If the system pressure is above the A/C pressure relief valve open pressure, REPAIR the system for a restriction.