Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSMERCURY2009MILAN PREMIER, 3.0 1, AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1680 (HVAC - CLIMATE CONTROL SYSTEM - GENERAL INFORMATION AND DIAGNOSTICS)DIAGNOSTIC TESTSCLIMATE CONTROL SYSTEMSYMPTOM CHART - CLIMATE CONTROL SYSTEMS

2009 Mercury Milan Premier, 3.0 1, AWD

Symptom Chart - Climate Control Systems

2009 Mercury Milan Premier, 3.0 1, AWDSECTION Symptom Chart - Climate Control Systems

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

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.
HVAC functions verification	HVAC system and/or related components	Go to Pinpoint Test M .
The air inlet door is inoperative	Circuitry open/shorted Door actuator Air inlet door binding or stuck HVAC module	Go to Pinpoint Test K .
Incorrect/erratic direction of airflow from outlets	Circuitry open/shorted Door actuator Mode door binding or stuck HVAC module	Go to Pinpoint Test L .
The steering wheel control switch is inoperative/does not operate correctly	Circuitry short/open Steering wheel control switch HVAC module	Go to Pinpoint Test G .
Insufficient air conditioning (A/C) cooling	Restricted A/C evaporator core orifice Low refrigerant level A/C cycling switch Evaporator discharge air temperature sensor Temperature blend door actuator control	Go to Refrigerant System Tests .
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 P . If the A/C compressor cycles normally, go to Pinpoint Test Q .
Insufficient, erratic or no heat	Low engine coolant level Engine overheating Plugged or partially plugged heater core Temperature blend door binding or stuck A/C electric blend door actuator Blend door circuit open/shorted	Go to Pinpoint Test N .
The air conditioning (A/C) is inoperative	Fuse(s) A/C clutch relay Circuitry short or open A/C cycling switch A/C system discharged or low charge A/C compressor clutch A/C evaporator discharge air temperature sensor A/C pressure sensor HVAC module PCM	Go to Pinpoint Test O .
The air conditioning (A/C) is always on - A/C compressor does not cycle	Circuitry short or open HVAC module A/C clutch relay A/C compressor clutch A/C evaporator core temperature sensor	Go to Pinpoint Test P .
The air conditioning (A/C) is always on - A/C mode always commanded ON	Circuitry short or open HVAC module A/C clutch relay A/C compressor clutch A/C evaporator core temperature sensor	Go to Pinpoint Test Q .
The blower motor is inoperative	Fuse(s) Circuitry open or shorted Blower motor Blower motor speed control Blower motor relay	Go to Pinpoint Test R .
The blower motor does not operate correctly	Blower motor speed control HVAC module Circuit short or open	Go to Pinpoint Test S .
The temperature set point does not repeat after turning the ignition switch OFF	Fuse Circuitry short or open HVAC module	VERIFY Central Junction Box (CJB) fuse 27 (10A) is OK. If OK, CHECK circuit 1566 (RD/YE) for an open and REPAIR as necessary. If OK, INSTALL a new HVAC module. If not OK, REFER to SYSTEM WIRING DIAGRAMS article to identify the possible causes of the circuit short.
The electronic automatic temperature control is inoperative/does not operate correctly	Temperature blend door/actuator broken/binding HVAC module	CHECK the temperature blend doors/actuators for a binding or broken condition. If no condition is found, INSTALL a new HVAC module.
The temperature display will not switch between Celsius and Fahrenheit	HVAC module	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 the Ambient Temperature Sensor component test under Component Tests . If the sensor tests OK, INSTALL a new HVAC module. 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.

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.