H4 vs. Older Sealed-Beam Headlight Wiring
H4 and some older sealed-beam headlights use three terminals, but the ground and low-beam connections are in different positions. Check the wiring before installing replacement HID or LED headlights.
H4 and Sealed-Beam Wiring Diagram
Compare the terminal locations for H4 and the older H4666 / H6545 / H4668 sealed-beam configuration shown below.
Diagram orientation is as shown above. Looking at the back of a connector may reverse left and right. Always verify the physical connector and vehicle wiring.
Quick Wiring Comparison
| Terminal in diagram | H4 | Older sealed beam shown |
|---|---|---|
| Top center | Low beam (+) | Ground (−) |
| Left | High beam (+) | High beam (+) |
| Right | Ground (−) | Low beam (+) |
Problem
After installing an H4 HID or LED headlight in an older vehicle, the low beams may not turn on or the headlights may work incorrectly.
Solution
Check the ground, high-beam and low-beam terminals. For the sealed-beam configuration shown, the ground and low-beam positions differ from H4. Use the correct adapter or have the connector rewired to match the verified H4 pinout.
