New H4 Wiring Harness wiring issue

[carguy996]

I have a 2002 Mitsubishi Eclipse, the previous owner replaced the wiring harness for both headlights and I think there might be an issue with the wiring. When the low beams are on the left headlight looks normal but the right headlight is a bright focused beam, with the highbeams on, the left headlight sppears to go to high beam and the right headlight doesnt appear to do anything. There is a black a white and a red wire on the harness. Should I switch the red and white wire to see if that fixes the issue?

Thanks!

 

[Hokiefyd]

Carguy996, first check to ensure that the bulbs are oriented correctly in the housing. What you describe sounds like an H4 bulb that is not "clocked" correctly in the housing. As installed, the glare shield "cup" in the bulb should sit BELOW the front filament, not to the side or on top of it.

 

[JHZR2]

Not sure how it could be clocked wrong unless some of the tabs were removed or damaged. If wired wrong, it would be possible for the bulb to somehow take some circuitous route to ground through both fillaments, I guess.

 

[carguy996]

It looked like the bulb was installed correctly but I will double check. I tried disconnecting the harness from the bulb and it appeared to be stuck on there pretty good. Ill work on it more this evening.

 

[Hokiefyd]

I've seen a number of vehicles that have H4 bulbs that look "odd" in one side. Like the beam pattern is all messed up. There are bright spots and dark spots in the lamp, so it's not on high beam. Some H4 retention systems aren't great, so you might have one in "crooked" as well, or not seated properly.

A sure-fire way to test the harness is to check voltage when power is applied via the switch. Put probes of a volt meter set to (D)irect(C)urrent on the top pin and the left side pin (as seen in the photo below) and look for at least 12V with the switch on. The ground (common) and high pins together should have no voltage with the low beams on.

When you reinstall, you can apply some dielectric grease to the pins for easier disassembly next time.

Source: http://www.ohio.edu/people/ridgely/Photos and stuff/H4_Pinout.jpg

 

[carguy996]

Thank you for this information, I removed the bulb and it was indeed not seated properly, I reseated the bulb and reconnected it and the headlight now shines properly!

 

[Hokiefyd]

Excellent. Great news!