Lexus IS300 Turn Signal Bulb Size

Additional Notes

• The 7440NA is the most frequently specified bulb across the Lexus IS300 turn signal positions. It is a single-filament T20 wedge bulb rated at 12V and 21W, with natural amber glass that produces the required amber signal color without relying on a colored lens or housing.
• The 7440NA differs from the standard 7440 in one key respect: the "NA" suffix denotes natural amber glass, meaning the bulb envelope itself is tinted amber. The 7440 carries a clear glass envelope and depends on an amber lens to produce the correct signal color.
• The 7444NA and 7443NA are dual-filament T20 wedge bulbs rated at 12V, 21W/5W. The higher wattage filament serves the turn signal function, while the lower wattage filament supports a secondary function such as a parking or daytime running light within the same housing.
• Although the 7444NA and 7443NA share the same T20 wedge form factor and wattage ratings as the 7440NA, their dual-filament construction means they are not interchangeable with single-filament 7440NA sockets without risking incorrect circuit behavior.
• The Lexus IS300 (2016 and 2019) specifies the 7444NA for the front turn signal position, while surrounding model years use the single-filament 7440NA, indicating that the front housing in those years incorporated a combined lighting function requiring the dual-filament design.
• The PY21W, specified for the 2001 IS300 rear turn signal, follows the ECE standard rather than the ANSI standard used by all other bulbs in these specifications. It uses a BAU15s bayonet base, which is physically distinct from the T20 wedge base, making it incompatible with sockets designed for the 7440 series.
• The ECE and ANSI standards govern different regulatory markets. ECE applies to Europe and most international markets, while ANSI applies to the United States and Canada. The shift from PY21W to 7440-series bulbs in later IS300 model years reflects a change in the base standard used for the vehicle's lighting components in the North American market.
• All bulbs listed across both turn signal positions operate at 12V, which is consistent with standard 12-volt automotive electrical systems. The primary filament wattage of 21W is uniform across every bulb type specified, regardless of filament count or base type.