Symptom Chart - Climate Control Systems

WARNING: This page is about a different car, the 2013 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 ENGINE CONTROLS - INTRODUCTION (EXCEPT DIESEL & HYBRID) (SECTION 0) .

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	If the A/C compressor does not cycle, GO to PINPOINT TEST N .
Reduced outlet airflow	A/C compressor clutch air gap A/C pressure transducer Evaporator discharge air temperature sensor A/C clutch relay Blower motor Blower motor control PCM	If the A/C compressor cycles normally, GO to PINPOINT TEST R .
The air inlet door is inoperative	Circuitry open/shorted Air inlet mode 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 Mode door actuator(s) Mode door(s) binding or stuck HVAC module	GO to PINPOINT TEST K .
Insufficient, erratic or no heat	Low engine coolant level Plugged or partially plugged heater core Temperature blend door(s) binding or stuck Temperature blend door actuator(s)	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 compressor 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 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	HVAC module	INSTALL a new HVAC module. REFER to CLIMATE CONTROL .
Inaccurate external temperature display	HVAC module Ambient temperature sensor	GO to PINPOINT TEST E .
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.