The Isuzu EVR uses the 1156 Heavy Duty bulb in both the front and rear turn signal positions across all listed model years, 1987-1993.
The 1156 is a single-filament bulb, meaning it serves one lighting function rather than combining two, such as stop and tail, into a shared housing.
The 1156 operates at 12 volts and 21 watts, which places it in the standard range for automotive turn signal applications.
The bulb uses a BA15s bayonet base, a single-contact fitting that locks into the socket with a twist and is not interchangeable with dual-contact bayonet bases such as the BA15d.
The 1156 conforms to ANSI standards recognized in both the United States and Canada, indicating a standardized specification for the bulb's electrical and physical characteristics.
The Heavy Duty designation indicates a construction built to withstand greater vibration and thermal stress compared to a standard 1156, though the base type, voltage, and wattage remain the same.
Because the Heavy Duty variant shares the same BA15s base and 12V/21W rating as a standard 1156, physical fitment is compatible, but the duty rating differs between the two variants.