my Ford Mustang S550 (2015-2023) battery dies after sitting for a few days

Solution

1. Preparation

• Gather necessary tools and safety equipment.
• Tools Required: Multimeter, OBD-II scanner, Battery load tester, Basic hand tools (wrenches, sockets).
• Safety Warning: Disconnect the battery before working on electrical systems.

2. Identify Parasitic Draw

• Sub-step 1: Disconnect the negative battery terminal.
• Sub-step 2: Set the multimeter to the 10A DC setting. Connect the multimeter in series between the negative terminal and the negative battery cable.
• Sub-step 3: Record the current reading. A draw above 50mA indicates a potential issue.
• Sub-step 4: Pull fuses one at a time while monitoring the multimeter until the current draw drops significantly, indicating the circuit causing the draw.

3. Repair Identified Issue

• Sub-step 1: If a specific circuit is causing the draw, inspect the components on that circuit (e.g., lights, modules) for faults or shorts.
• Sub-step 2: Repair or replace any faulty components as necessary.
• Sub-step 3: If the battery is found to be faulty, replace it with a new, properly rated battery for the Mustang S550.

4. Reassemble and Test

• Sub-step 1: Reconnect the negative battery terminal securely.
• Sub-step 2: Clear any diagnostic trouble codes using the OBD-II scanner.
• Sub-step 3: Start the vehicle and verify that all electrical components function normally.