The power window fuse symbol on an automotive fuse box cover is a standard ISO/SAE fuse icon (a rectangle bisected by a horizontal line) paired with either a window graphic (a square with an internal chevron) or the text abbreviations 'P/WDW', 'WIN', or 'DOOR'. In 90% of modern vehicles, this circuit requires a 20A (yellow), 25A (clear/white), or 30A (green) ATO/ATC blade fuse. If your vehicle uses a multiplexed Body Control Module (BCM), the symbol may instead read 'BCM' or 'PWR ACC'.
Power Window Fuse Symbol & Rating Reference Table
Use this table to decode the legend on your fuse box cover. The amperage and color codes follow the SAE J1284 and ISO 8820 standards for automotive blade fuses.
| Symbol / Graphic | Text Label | Typical Amps | Fuse Color | Application & Wire Gauge |
|---|---|---|---|---|
| Rectangle + Chevron | P/WDW or P/W | 20A | Yellow | Standard 4-door sedan (all windows); 12 AWG wire |
| Rectangle + 'W' | WIN or WND | 25A | Clear / White | European models (VW/Audi) with auto-up/down logic; 12 AWG |
| Rectangle + 'D' | DOOR or PWR DR | 30A | Green | Trucks/SUVs with heavy motors or integrated seat memory; 10 AWG |
| Rectangle + Lock Icon | W/LCK | 10A | Red | Window lock switch circuit only (does not power motors); 16 AWG |
| Rectangle + Microchip | BCM or ECU-IG | 15A / 20A | Blue / Yellow | Multiplexed systems where the BCM drives solid-state window relays |
Automotive Standards: SAE, ISO, and JASO Variants
Unlike household wiring governed by the NEC or IEC, automotive electrical systems rely on regional engineering standards. The physical shape of the fuse and the way the symbol is presented depend heavily on where the car was engineered.
- North America (SAE): Typically uses the text abbreviation 'P/WDW' and standard ATO blade fuses. The fuse symbol is a simple rectangle with a horizontal line through the center.
- Europe (ISO/DIN): Prefers graphic symbols over text. You will see a square with an upward/downward chevron inside it. European cars heavily utilize Micro2 and Mini fuses to save space on the fuse board, often dedicating a separate 15A or 20A fuse for each individual door rather than one master fuse.
- Japan (JASO): Often labels the circuit 'DOOR' or 'P/W'. Because Japanese automakers historically wired all four window motors to a single master relay, they frequently use 30A or 40A slow-blow (time-delay) fuses to handle the massive cumulative inrush current when multiple windows are rolled down simultaneously.
Rows People Get Wrong (Common Misidentifications)
Automotive fuse box legends are notoriously cramped. Misinterpreting a symbol can lead to repeated blown fuses or chasing a ghost electrical fault.
Mistake 1: Confusing 'W/LCK' with the Motor Fuse
The 'W/LCK' (Window Lock) fuse is typically a 10A red fuse. It does not power the window motors. It only powers the ground-path interrupt switch on the driver's door master panel. If your passenger windows won't roll down from the passenger doors, but work from the driver's door, do not check the W/LCK fuse—check the passenger door module or the LIN-bus communication wire.
Mistake 2: Using Fast-Blow Fuses on Slow-Blow Circuits
Window motors are inductive loads. When a window motor starts, or when it hits the physical travel limit (stall current), it can draw 2.5 to 3 times its normal running current for a few hundred milliseconds. If your vehicle's manual specifies a time-delay (slow-blow) fuse and you replace it with a standard fast-blow ATO fuse of the same amperage, it will blow immediately upon startup. Always check the fuse blade for a tiny 'S' or 'Z' stamped into the plastic, indicating a time-delay element.
Mistake 3: The 'Multiplexed' Ghost Fuse
In vehicles built after 2015, you might not find a 'P/WDW' symbol at all. Modern architectures use a Body Control Module (BCM). The window switch simply sends a low-voltage digital signal to the BCM, which then triggers a solid-state relay to send 12V to the motor. If you have no window power and no 'P/WDW' fuse, look for the 'BCM' or 'PWR ACC' fuse.
Decision Path: Sizing and Replacing the Fuse
When a power window fuse blows, it is almost always due to a mechanical bind in the window track causing the motor to exceed its stall current threshold, or a short in the door-jamb wiring boot. Never upsize a fuse to stop it from blowing. Follow this decision tree to select the correct replacement.
| Condition / Symptom | Diagnostic Action | Concrete Replacement Pick |
|---|---|---|
| Standard ATO fuse blew; wire in harness is 12 AWG. | Inspect door jamb rubber boot for pinched wires. If clear, replace fuse. | Littelfuse ATOF 20A Yellow (Part # 0287020.PXCN) |
| Standard ATO fuse blew; wire in harness is 10 AWG (Trucks/SUVs). | Check window regulator cables for fraying. Replace fuse. | Littelfuse ATOF 30A Green (Part # 0287030.PXCN) |
| Compact fuse required; European vehicle with Micro2 slots. | Verify it is not a Mini (ATM) fuse. Micro2 has asymmetrical blades. | Littelfuse Micro2 20A Yellow (Part # 0297020.WXNV) |
| Fuse blows instantly upon replacement. | Stop. You have a dead short to ground. Unplug the window motor and test the harness for continuity to chassis ground. | Do not install another fuse until the short is cleared. |
Safe Interpretation When Markings Are Faded or Missing
If you are working on an older project car, a salvage yard pull, or a fleet vehicle where the fuse box cover legend is sun-baked and illegible, you must identify the correct fuse electrically. Do not guess by pulling fuses while the ignition is off.
- Establish the Power State: Most power window circuits are ignition-switched or accessory-switched. Turn the key to the 'ACC' or 'RUN' position. Do not start the engine to avoid alternator voltage spikes during testing.
- Use a Test Light or Multimeter: Set your multimeter to DC Voltage. Probe the test points on the top of the blade fuses (most ATO/Mini fuses have two small exposed metal pads on the top face). You are looking for a fuse that has 12V on one side, but 0V on the other (indicating it is blown), or 12V on both sides (indicating it is intact and passing power).
- The Voltage Drop Test: If you suspect a fuse is failing internally but hasn't fully blown (common with cheap aftermarket fuses that develop micro-cracks in the element), set your multimeter to DC millivolts. Place the probes across the two test points of the fuse while operating the window. A healthy fuse will read less than 50mV. If you read >200mV, the fuse element is degrading and must be replaced.
- Trace the Load: If you cannot find a fuse with 12V, pull the driver's door master switch panel. Identify the thick 12V+ power wire (usually red, blue, or green depending on the OEM wiring standard). Use a tone generator or continuity tester to trace that wire back to the fuse box, checking fuses for continuity until you find the match.
By matching the physical symbol on the cover to the correct SAE/ISO standard and verifying the wire gauge, you can confidently select the exact Littelfuse or Bussmann replacement part without risking damage to the vehicle's door harness or Body Control Module.
