H4 / 9003 / HB2 Lamp Socket Adapter Wiring Harness – Female Plug Connector Extension Cable (4 Pcs)

A set of 4 H4 / 9003 / HB2 lamp socket adapter wiring harnesses with female plug connectors and extension cables. Used for headlight bulb socket repair, HID/LED conversion harness adaptation, and headlight wiring extension on vehicles using the H4 / 9003 / HB2 bulb standard.

Key Specifications

• Bulb Standard: H4 / 9003 / HB2 (all three designations refer to the same bulb type)
• Pin Count: 3 (high beam, low beam, ground)
• Gender: Female socket (plugs onto H4 bulb base)
• Wire Gauge: 18 AWG (0.5 mm²)
• Wire Length: Extension cable included
• Housing Material: PA66 nylon (heat-resistant)
• Terminal Material: Copper alloy, tin-plated
• Current Rating: Up to 15A per pin (suitable for 55W/60W H4 halogen bulbs)
• Package: 4 pcs

H4 / 9003 / HB2 – Same Bulb, Three Names

• H4: European ECE designation (used in Europe, Asia, Australia)
• 9003: SAE/DOT designation (used in North America)
• HB2: ANSI designation (used in technical specifications)
• All three designations refer to the identical dual-filament bulb with the same 3-pin P43t base

Applications

• Headlight bulb socket repair – melted or corroded H4 socket replacement
• HID xenon conversion harness – H4 to HID ballast adapter
• LED headlight conversion – H4 LED bulb socket adapter
• Headlight wiring extension – additional cable length for custom installations
• Universal fit for any vehicle using H4 / 9003 / HB2 headlight bulbs

H4 Socket Failure – Common Causes

• Melted socket: Caused by loose terminal contact creating resistance heat – replace socket immediately to prevent wiring harness damage
• Corroded terminals: Moisture ingress causes green oxidation on copper terminals – clean with contact cleaner or replace socket
• Intermittent headlight: Loose terminal in H4 socket – wiggle test confirms socket fault

FAQ

Q: Are H4, 9003, and HB2 the same bulb socket?
A: Yes. H4 (ECE), 9003 (SAE), and HB2 (ANSI) all use the identical P43t 3-pin base. This adapter is compatible with all three designations.

Q: Can I use this adapter for LED headlight conversion?
A: Yes. This H4 socket adapter is compatible with H4-base LED headlight bulbs. Ensure the LED bulb's power draw does not exceed 15A per pin.

Q: Why does my H4 socket melt?
A: H4 socket melting is caused by loose terminal contact. A loose terminal creates resistance, which generates heat proportional to current × resistance. A 55W H4 bulb draws approximately 4.6A – even 0.5Ω of contact resistance generates 10.6W of heat at the terminal, sufficient to melt the PA66 housing.

Package Contents

4 × H4 / 9003 / HB2 Female Lamp Socket Adapter with 18 AWG extension wire