Symptom Chart - Climate Control Systems

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. 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 Engines article.

Condition	Possible Sources	Action
No communication with the HVAC module	Fuse(s) Circuitry short/open HVAC module communication network	REFER to MODULE COMMUNICATIONS NETWORK article to continue diagnosis of the communication network.
The EATC system is inoperative, intermittent or incorrect operation	Fuse(s) Circuitry short/open HVAC module	Go to Pinpoint Test E .
Incorrect/erratic direction of airflow from outlets - manual climate control	No vacuum to the A/C control Function selector switch Vacuum hose kinked/pinched Airflow door binding/stuck Vacuum control motor A/C vacuum check valve A/C vacuum reservoir tank and bracket Vacuum actuator arm not connected to the door crank	Go to Pinpoint Test F .
Incorrect/erratic direction of airflow from outlets - EATC	HVAC module No vacuum to the A/C control Vacuum hose kinked/pinched Airflow door binding/stuck Vacuum control motor A/C vacuum check valve A/C vacuum reservoir tank and bracket Vacuum actuator arm not connected to the door crank	Go to Pinpoint Test G .
Insufficient, erratic or no heat	Low engine coolant level Engine overheating Plugged or partially plugged heater core Temperature blend door binding/stuck Temperature blend door actuator	Go to Pinpoint Test H .
The air conditioning (A/C) is inoperative/does not operate correctly	Fuse(s) Circuitry short/open A/C cycling switch A/C system discharged/low charge A/C pressure cutoff switch HVAC module Function selector switch	Go to Pinpoint Test I .
Insufficient air conditioning (A/C) cooling	Low refrigerant level Temperature blend door actuator	CARRY OUT the refrigerant system tests. REFER to Refrigerant System Tests . If OK, go to Pinpoint Test A for vehicle equipped with EATC, or if equipped with manual climate control, Go to Pinpoint Test K .
The air conditioning (A/C) is always on	Circuitry short/open A/C control relay HVAC module Function selector switch	Go to Pinpoint Test J .
Temperature control is inoperative/does not operate correctly - manual climate control	Temperature blend door actuator control Temperature blend door Temperature blend door actuator motor Circuitry open/shorted	Go to Pinpoint Test K .
The blower motor is inoperative - manual climate control	Fuse(s) Circuitry open/shorted A/C blower motor switch A/C blower motor resistor A/C blower motor	Go to Pinpoint Test L .
The blower motor is inoperative - EATC	Fuse(s) Circuitry short/open Blower motor relay A/C blower motor A/C blower motor speed control	Go to Pinpoint Test M .
The blower motor does not operate correctly - manual climate control	Circuitry short/open A/C blower motor resistor A/C blower motor switch	CARRY OUT the Resistor - Blower Motor . If the blower motor resistor tests good, go to Pinpoint Test N .
The blower motor does not operate correctly - EATC	Circuitry short/open A/C blower motor speed control HVAC module	Go to Pinpoint Test O .
The steering wheel control switch is inoperative/does not operate correctly	Circuitry short/open Steering wheel control switch HVAC module	Go to Pinpoint Test P .
The temperature set point does not repeat after turning the ignition switch OFF - EATC	Fuse(s) Circuitry short/open HVAC module	CHECK circuit 1566 (RD/YE) for a short or open and repair as necessary. If OK, INSTALL a new HVAC module.
The temperature display will not switch between Celsius and Fahrenheit - EATC	HVAC module	PRESS the MAX A/C and DEFROST buttons simultaneously for at least 0.75 second. If the temperature display does not switch between Celsius and Fahrenheit, INSTALL a new HVAC module.
Inaccurate external temperature display	HVAC module	REFER to description and operation of the HVAC External Temperature Display . If the external temperature display is not operating as described and no DTC is present, CARRY OUT Temperature Sensor - Ambient . If the sensor tests OK, INSTALL a new HVAC module. REFER to CLIMATE CONTROL article. TEST the system for normal operation.