The air conditioning system in a Ford Mustang aims to provide stable and consistent cooling airflow to passengers. However, some models encounter issues with fluctuating blower fan speeds that fail to maintain steady air circulation.
This article examines the causes of this inconvenient A/C problem and provides reliable diagnostic and repair information for technicians. Details on vehicle model years affected, faulty components, and cost estimates are also discussed.
Problem Explanation
The issue of the A/C fan speed changing unpredictably is a common problem in certain model years of the Ford Mustang. This problem is often characterized by the fan blowing at inconsistent and fluctuating speeds when the A/C system is engaged, rather than maintaining a steady airflow.
This problem is typically caused by a failing blower motor resistor or a faulty A/C fan control module. The blower motor resistor controls the voltages supplied to the blower fan, regulating the different fan speeds. When it fails, it can cause irregular power signals resulting in inconsistent fan operation. Similarly, the A/C fan control module dictates the blower motor speed based on various temperature and environmental inputs. Faults in this control module can also lead to irregular fan speeds.
Diagnostic Procedures
Tools and Equipment:
- Voltmeter
- Wiring schematics
- Diagnostic scanners
Diagnostic Steps:
1. Visually inspect the blower motor resistor for signs of damage, overheating or burnt terminals. Replace if faulty.
2. Using a voltmeter, check for power and ground at blower motor resistor terminals during A/C operation. Compare voltages to specified values on wiring diagram.
3. With a diagnostic scanner, check for any related trouble codes stored in the A/C fan control module that could explain irregular fan operation.
4. Monitor A/C fan control module sensor inputs including evaporator temperature sensor, sunlight sensor, in-car temperature sensor. Inspect sensors and replace any that are out of specification.
5. If no defects found, replace A/C fan control module and retest system operation.
Repair Solutions
The most common repair solutions include:
- Replacing the faulty blower motor resistor
- Replacing damaged or worn-out wiring and connectors
- Replacing the A/C fan control module if diagnosed as defective
- Updating the A/C fan control module software/firmware if applicable
Ford Mustang Model Years Potentially Impacted
This issue is most commonly reported in 2005-2009 Ford Mustang models but may potentially affect other model years.
Vehicle Components Potentially Affected
- Blower motor resistor
- Wiring and connectors
- A/C control module
- Blower motor
- Various sensor inputs to A/C control module
Cost of Repairing This Issue
The average cost for repairs often ranges from $200 – $350 in parts and labor. Blower motor resistor replacement alone typically costs $150-250. For control module or wiring harness replacement, costs may exceed $500 in some cases.
Prices can vary depending on part costs and hourly labor rates. Diagnosing the specific cause of the issue also impacts repair costs.
John Smith, a Los Angeles-based car specialist and automotive writer, boasts over 20 years in the industry. With a background as a master technician and a decade-long writing stint at notable automotive publications, John now shares his expansive knowledge on CarFinite, simplifying car maintenance for readers.