Locate the power distribution center under the hood near the battery and match each numbered slot with its assigned circuit using the label inside the cover. Confirm slot numbers before removing any component to avoid interrupting ignition, lighting, or fuel system operation.
Use a multimeter or test light to check voltage on both terminals of each blade insert. A working element will show continuity, while a failed one interrupts current flow and can disable systems such as power windows, radio, or engine control modules.
Amperage ratings typically range from 10A for interior electronics to 50A for high-load systems like cooling fans or power accessories. Install replacements with identical ratings only to prevent overheating wires or damaging connected components.
Inside the cabin, the junction unit located beneath the dashboard controls interior circuits and relays. Swap identical relays between circuits as a quick diagnostic method to determine whether a fault is caused by a relay or wiring issue.
1999 Mustang GT Fuse Box Diagram with Locations and Circuit Details
Check the engine compartment power distribution center first, then match each numbered slot with the legend printed under the cover; this prevents removing the wrong component and interrupting circuits like ignition or fuel delivery.
The under-hood unit contains high-current circuits ranging from 30A to 50A, supplying systems such as cooling fan, ABS module, and charging circuit, while the interior junction block handles lower-load electronics like radio, interior lighting, and dashboard controls.
Typical circuit grouping
- Cooling fan and engine control circuits placed near the front section
- Exterior lighting circuits aligned along one side
- Power window and seat circuits located in central rows
- Accessory and audio circuits inside the cabin unit
Each cavity is labeled with a number and function code, which should be cross-checked with service documentation or the cover label to ensure accurate identification during troubleshooting.
Relays positioned рядом with these inserts control high-load components such as starter motor, horn, and fuel system; swap identical relay units from non-critical circuits to quickly confirm whether the issue is caused by the relay or wiring.
Exact location of interior and engine bay fuse boxes in 1999 Mustang GT
Open the hood and locate the main power distribution unit on the driver-side front corner near the battery; this is the primary point for high-current protection covering systems like cooling fan, ABS, and charging circuit.
The plastic cover snaps off by releasing two side clips, revealing rows of large blade inserts and relays arranged in a rectangular layout. Use the underside label to identify each slot before removal to avoid disabling critical systems.
Inside the cabin, the secondary panel sits beneath the dashboard on the driver side, slightly left of the steering column and above the footwell area. Access requires removing a trim panel or pulling down a cover.
This interior unit handles lower-amperage circuits such as radio, instrument cluster, interior lighting, and power locks, with ratings typically between 5A and 25A depending on the circuit load.
Access tips for both panels
Keep a flashlight ready, as the cabin-mounted panel is recessed and not directly visible from a seated position. Lie back in the driver footwell to get a clear view of slot numbering and labels.
In the engine compartment, ensure the ignition is off and the key removed before opening the cover; moisture or dirt around the housing should be cleaned to prevent contamination when accessing components.
Position reference points
The under-hood unit aligns with the battery and fender edge, while the interior panel aligns with the brake pedal assembly and lower dash frame, making both easy to locate once familiar with these anchor points.
Verify placement by matching wire harness bundles; thicker harnesses route into the engine bay unit, while smaller grouped wires feed into the cabin-mounted panel.