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.

2008 Ford Mustang GT, 2D Convertible, AutomaticFACTORY OEM SERVICE PROCEDURE

Symptom Chart - Climate Control Systems

NOTE: Some PCM DTCs may inhibit A/C operation. If any PCM DTCs are retrieved, diagnose those first. Refer to the PCM DTC Chart

Condition	Possible Sources	Action
HVAC functions verification	HVAC system and/or related components	Go to Pinpoint Test K .
The air inlet mode door is inoperative	Circuitry short/open HVAC module Air inlet mode door actuator/linkage	Go to Pinpoint Test C .
Incorrect/erratic direction of airflow from outlet(s)	Circuitry Door actuator Mode door binding or stuck HVAC module Door actuator arm not connected to the door crank	Go to Pinpoint Test D .
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 E .
The air conditioning (A/C) is inoperative	Fuse Circuitry short/open A/C system discharged/low charge Dual-function pressure switch PCM Smart Junction Box (SJB) HVAC module A/C cycling switch A/C compressor clutch air gap A/C clutch relay	Go to Pinpoint Test F .
The air conditioning (A/C) is always on - A/C compressor does not cycle	Circuitry short PCM SJB A/C compressor clutch air gap A/C cycling switch A/C clutch relay	Go to Pinpoint Test G .
The air conditioning (A/C) is always on - A/C mode always commanded ON	Circuitry short PCM SJB	Go to Pinpoint Test H .
Temperature control is inoperative/does not operate correctly	Circuitry open/shorted HVAC module Temperature blend door Temperature blend door actuator	Go to Pinpoint Test D .
The blower motor is inoperative	Fuse(s) Circuitry open/shorted A/C blower motor switch Blower motor relay A/C blower motor	Go to Pinpoint Test I .
The blower motor does not operate correctly	Circuitry short A/C blower motor resistor A/C blower motor switch	Go to Pinpoint Test J .
Reduced outlet airflow	Circuitry short A/C compressor clutch air gap A/C cycling switch A/C clutch relay Blower motor Blower motor resistor Blower motor resistor PCM SJB	If the A/C compressor does not cycle, go to Pinpoint Test G . If the A/C compressor cycles normally, go to Pinpoint Test J .
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.

Factory Service Tools

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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.

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