1. Diagnose the Problem:
* Window doesn't move at all: This suggests a problem with the power switch, the window regulator, or the motor.
* Window moves slowly or intermittently: Likely a problem with the motor, regulator, or worn-out components within the regulator.
* Window moves, but only in one direction: This usually points to a faulty switch or a problem with the regulator mechanism.
* Window makes a clicking or grinding noise: Indicates a problem with the motor or the regulator, possibly a binding track.
* Window only works sometimes: Could be a loose connection, corroded wire, or a failing switch.
2. Troubleshooting Steps:
* Check the fuses: Consult your owner's manual to locate the fuses for the power windows. Replace any blown fuses.
* Inspect the window switches: Try all the switches (driver and passenger). If the problem only occurs with one switch, it's likely the switch itself is faulty. Try cleaning the switch contacts with contact cleaner.
* Check the wiring: Look for broken, frayed, or corroded wires in the door harness, especially around the flexing points where the door hinges. This is a common failure point.
* Test the window motor: This usually requires partially disassembling the door panel to access the motor. You can try applying 12V directly to the motor terminals (carefully!) to see if it runs. Caution: Improperly applying power can damage the motor. If you're not comfortable with this, seek professional help.
* Inspect the window regulator: This is a more involved process requiring complete door panel removal. The regulator mechanism can wear out, break, or become jammed with debris. Inspect the tracks, cables, and moving parts for damage or binding.
* Listen for unusual sounds: Grinding or clicking noises point to a failing motor or regulator.
3. Common Parts That Fail:
* Window Switch: Relatively inexpensive and easy to replace.
* Window Regulator: More expensive and requires more work to replace. Often sold as a complete assembly (motor and regulator).
* Window Motor: Can be replaced separately, but often comes as part of the regulator assembly.
* Wiring Harness: Repairing or replacing sections of the harness can be challenging.
4. Repair or Replacement:
* Switch Replacement: Relatively straightforward DIY repair with readily available replacement switches.
* Regulator and/or Motor Replacement: More difficult DIY repair requiring significant disassembly of the door panel. You'll need tools, patience, and potentially some mechanical aptitude. Replacement parts are readily available online or from auto parts stores.
* Professional Repair: If you're uncomfortable performing the repair yourself, take it to a qualified mechanic or auto electrician.
Important Considerations:
* Safety First: Disconnect the battery negative terminal before working on any electrical components.
* Consult a Repair Manual: A repair manual specific to your 2003 Mustang GT will provide detailed diagrams and instructions for accessing and replacing the various components.
* Online Resources: Many online forums and YouTube videos demonstrate the repair process for Mustang power windows.
Without knowing the precise symptoms, this is the most comprehensive guidance possible. Start with the simplest troubleshooting steps (fuses and switches) and progress to the more complex ones (regulator and motor inspection) as needed. If you're not comfortable working on car electronics, seeking professional help is always the best option.
