Symptom Chart - Climate Control Systems

WARNING: This page is about a different car, the 2008 Mercury Sable, 2008 Ford Taurus X, and 2008 Ford Taurus. 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 -Dual Automatic Temperature Control (DATC) or HVAC module - Electronic Manual Temperature Control (EMTC)	Fuse(s) Circuitry open HVAC module communication network	REFER to MODULE COMMUNICATIONS NETWORK article.
HVAC functions verification	HVAC system and/or related components	Go to Pinpoint Test G .
The air inlet door is inoperative	Circuitry open/shorted Door actuator Air inlet door binding or stuck HVAC module - EMTC or HVAC module - DATC	Go to Pinpoint Test H .
Incorrect/erratic direction of airflow from outlets	Circuitry open/shorted Door actuator Mode door binding or stuck HVAC module - EMTC or HVAC module - DATC	Go to Pinpoint Test I .
Reduced outlet airflow	Circuitry short A/C compressor clutch air gap A/C cycling switch A/C clutch relay Blower motor Blower motor control Blower motor resistor Blower motor switch PCM	If the A/C compressor does not cycle, go to Pinpoint Test L . EMTC systems, If the A/C compressor cycles normally, go to Pinpoint Test P . DATC systems, If the A/C compressor cycles normally, go to Pinpoint Test R .
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 J .
The air conditioning (A/C) is inoperative	Fuse(s) Circuitry open A/C system discharged/low charge PCM HVAC module - DATC HVAC module - EMTC A/C clutch relay A/C compressor clutch air gap A/C pressure transducer Evaporator discharge temperature sensor A/C clutch field coil	Go to Pinpoint Test K .
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	Go to Pinpoint Test L .
The air conditioning (A/C) is always on - A/C mode always commanded ON	Circuitry shorted PCM HVAC module - DATC HVAC module - EMTC A/C pressure transducer	Go to Pinpoint Test M .
Temperature control is inoperative/does not operate correctly	Circuitry open/shorted HVAC module - EMTC HVAC module - DATC Temperature blend door is binding or stuck Temperature blend door actuator	Go to Pinpoint Test N .
The blower motor is inoperative - EMTC	Fuse(s) Circuitry open A/C blower motor switch Blower motor relay A/C blower motor HVAC module - EMTC	Go to Pinpoint Test O .
The blower motor does not operate correctly - EMTC	Circuitry open/shorted A/C blower motor resistor A/C blower motor switch	Go to Pinpoint Test P .
The blower motor is inoperative - DATC	Fuse(s) Circuitry short/open Blower motor relay A/C blower motor HVAC module - DATC A/C blower motor speed control	Go to Pinpoint Test Q .
The blower motor does not operate correctly - DATC	Circuitry open/shorted A/C blower motor speed control HVAC module - DATC	Go to Pinpoint Test R .
The auxiliary blower motor is inoperative	Fuse(s) Circuitry open Auxiliary blower motor relay 1 Auxiliary blower motor resistor Auxiliary blower motor HVAC module - EMTC HVAC module - DATC	Go to Pinpoint Test S .
The auxiliary blower motor does not operate correctly	Fuse(s) Circuitry open/shorted Auxiliary blower motor relay 1 Auxiliary blower motor relay 2 Auxiliary blower motor relay 3 Auxiliary blower motor resistor Rear auxiliary control HVAC module - EMTC HVAC module - DATC	If the auxiliary blower motor does not operate correctly from both the front and rear auxiliary controls, go to Pinpoint Test T . If the auxiliary blower motor does not operate correctly from the rear auxiliary controls only, go to Pinpoint Test W . If the auxiliary blower motor does not operate correctly from the front auxiliary controls only, CARRY OUT the HVAC Module Cold Boot Process. If the condition returns, INSTALL a new HVAC module. REFER to CLIMATE CONTROL article. TEST the system for normal operation.
The auxiliary temperature control is inoperative/does not operate correctly using the front/rear auxiliary climate controls	Circuitry open/shorted Auxiliary blend door actuator HVAC module - EMTC HVAC module - DATC	If the auxiliary temperature control is inoperative/does not operate correctly from both the front and rear auxiliary controls, go to Pinpoint Test U . If the auxiliary temperature control is inoperative/does not operate correctly from the rear auxiliary controls only, go to Pinpoint Test W . If the auxiliary temperature control is inoperative/does not operate correctly from the front auxiliary controls only, CARRY OUT the HVAC Module Cold Boot Process. If the condition returns, INSTALL a new HVAC module. REFER to CLIMATE CONTROL article. TEST the system for normal operation.
The auxiliary panel/floor control is inoperative/does not operate correctly using the front/rear auxiliary climate controls	Circuitry open/shorted Auxiliary mode door actuator HVAC module - EMTC HVAC module - DATC	If the auxiliary panel/floor control is inoperative/does not operate correctly from both the front and rear auxiliary controls, go to Pinpoint Test V . If the auxiliary panel/floor control is inoperative/does not operate correctly from the rear auxiliary controls only, go to Pinpoint Test W . If the auxiliary panel/floor control is inoperative/does not operate correctly from the front auxiliary controls only, CARRY OUT the HVAC Module Cold Boot Process. If the condition returns, INSTALL a new HVAC module. REFER to CLIMATE CONTROL article. TEST the system for normal operation.
The auxiliary temperature, panel/floor and blower motor controls are inoperative/do not operate correctly using the front/rear auxiliary climate controls	Circuitry open/shorted Rear auxiliary control HVAC module - EMTC HVAC module - DATC	Go to Pinpoint Test W .
The temperature set point does not repeat after turning the ignition switch OFF	Fuse Circuitry short/open HVAC module - DATC	VERIFY Smart Junction Box (SJB) fuse 15 (10A) is OK. If OK, CHECK circuit SBP15 (WH/RD) for a short or open and repair as necessary. If OK, CARRY OUT the HVAC Module Cold Boot Process. If not OK, REFER to the Wiring Diagrams Manual to identify the possible causes of the circuit short. If the condition returns, INSTALL a new HVAC module - DATC.
The temperature display will not switch between Celsius and Fahrenheit	HVAC module - DATC Instrument Cluster (IC) module	If the IC does not switch between English and Metric, refer to INSTRUMENT CLUSTER AND PANEL ILLUMINATION article and diagnose. If only the HVAC module - DATC does not switch between English and Metric, CARRY OUT the HVAC Module Cold Boot Process. If the condition returns, INSTALL a new HVAC module - DATC.
Inaccurate external temperature display	HVAC module - DATC Ambient temperature sensor	REFER to description and operation of the HVAC module - DATC 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 - DATC. REFER to CLIMATE CONTROL article. 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.