Volvo XC70 Turn Signal Bulb Size

Additional Notes

• The PY21W is a single-filament amber bulb operating at 12V and 21W, built to ECE standards and fitted with a BAU15s bayonet base. It appears across multiple positions and model years in the Volvo XC70 turn signal specifications.
• The H21W follows the same ECE standard framework as the PY21W and shares the 12V, 21W rating, but uses a BAY9s base rather than a BAU15s base, making the two bulbs physically non-interchangeable despite their similar electrical ratings.
• The 1157NA is an ANSI-standard bulb used in North American markets. Unlike the ECE bulbs in these specifications, it carries a dual-filament design rated at 21W and 5W, with a BAY15d bayonet base and natural amber glass to meet amber signalling requirements without a painted or coated envelope.
• The 12496 is a Philips/Osram part number designating a 12V halogen bulb for specialty applications. It is not tied to a broad international standard designation in the way that PY21W or H21W are.
• The BAU15s base of the PY21W and the BAY15d base of the 1157NA are both 15mm bayonet-style fittings, but their offset pin configurations differ, preventing cross-installation between the two bulb types.
• The Volvo XC70 front turn signal position used the 1157NA for the 2004, 2006, and 2007 model years, then transitioned to the H21W from 2008 through 2016, reflecting a shift from an ANSI-standard dual-filament bulb to an ECE-standard single-filament type.
• The front inner turn signal position on the XC70 is only specified for the 2005-2007 model years, with the 2007 model using the 12496 and the 2005-2006 models using the PY21W.
• The rear turn signal position on the XC70 alternates between the PY21W and the 12496 across nearly every model year from 2003 through 2016, indicating that these two bulbs serve functionally equivalent roles in that position despite carrying different designation systems.
• Because the 1157NA is a dual-filament bulb and the PY21W, H21W, and 12496 are all single-filament types, substituting a dual-filament bulb into a socket wired for a single-filament application, or vice versa, would result in incorrect circuit behavior.
• The 2005 XC70 front turn signal uses the PY21W, while the 2004 model uses the 1157NA and the 2006 model also uses the 1157NA, making the 2005 model year an isolated exception within that three-year span for that position.