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Low Beam Headlight Problem

I own a 1989 Mazda 626 Turbo 2.2L. My passenger side low beam headlight went out. I replaced it with a new lamp (9004) and it still doesn’t work. Only the high beams work. I took it out and both of the filaments were fine. My drivers side low/high work. Help.

While I’m not familiar with your particular car, sometimes when the bulb socket itself develops corrosion, cleaning it with a small chunk of lightweight sandpaper or even scraping down the inside contacts with a pocket knife may solve the problem. Test the lamp with a vom meter for continuity on both filaments because sometimes you can’t see the break or take it back to the parts store and have them check it.

If those things don’t do it and the other low beam works fine, you may have a bad wire from the switch or an open circuit in a connector where the two lamps in the circuit split from a main feed. This is another area that you can troubleshoot with a vom meter and measure voltage along the circuit or starting from the connector and working your way back to the switch. Another handy and inexpensive tool to use if you’re without a vom, is a 12 v current probe that lights up with a proper ground and sesning 12 volts. You can pick up at just about any parts store.

thanks mark. i’m going to test the fuses today with a multimeter. i’ll let you know the results.

the fuses are fine. can it be the combination switch or the relay box?

If the lights are working, or you have power to the headlights, it’s not going to be a fuse problem. I believe you’ll find headlights (both) are on the same circuit. I’d take your meter and see if you’ve got power to the connector and if it’s got them, both contacts, one for high beam one for low. If the other low beam light works, I doubt it’s either the combination switch or relay. Again, this is one of those situations a current probe would be really helpful since a sharp tip will let you probe the wire past the insulation without causing any damage.

The only tricks are that you need a good ground on your clip and either a schematic or knowledge of where you should be seeing power in the circuit when the lights are turned on. Hope this helps.

this might sound funny but when i bought the car new(i’m the only owner) i bought the shop manual. i should be solving this problem but you need an engineering degree to understand all the complex diagrams, etc. Their all in here if you know what to look for. I’m 50/50 with it at this point. Anyway, what connector are you talking about? The one plugging into the 9004 lamp, or on the other end somewhere? If you tell me exactly what to probe, i got the info in the manual that tells me all the continuity, power, etc. Let me know. thanks for hanging in there with me Mark.