Calling All Car Junkies - What's wrong with my car?

[roadwreck]

I should join a car forum with all the crap I've been attempting to do to my cars lately. Last weekend was brakes on my car (which was a much bigger ordeal then it should have been), this week it's a headlight out on my wife's car. At first I thought the bulb was just burnt out and it'd be a simple fix...

...I should have learned after last weekends misadventure that no car project is ever simple. So here's my problem. I went ahead and replaced the bulb on the drivers side headlight but the new bulb still didn't work. Just to make sure that it wasn't a problem with the new bulb I pulled the passenger side bulb out and swapped it to the drivers side. Still no light. I also swapped the new bulb over the passenger side to see if it worked, it did. So I've ruled out a bulb problem. Next I went to the fuses and checked them all out. They all looked fine, but just to be sure I swapped all the headlight (hi & low beam) fuses out to rule that out as the problem. Still nothing, driver's side headlight still doesn't work. All the other lights work (parking, indicators, high beams, etc.) can anyone think of another reason one light would be out other then a wiring problem? I really don't want to fiddle with the wiring if I don't have to.

At this rate I think I need to sell my cars and start riding the bus.

 

[Master slacker]

1) What year / model is the car?

2) Use a voltmeter to make sure you have 12V from bulb socket to ground (turn lights on ).

It really shouldn't be that hard unless you have fancy-shmancy luxury car. Typically from your headlight switch, you'll go straight to the bulbs. Also, the two head lamps be wired to the same source. If you can find that source (since it obviously has 12V going to the other light) you should be able to narrow the range of sleuthing. HTH

 

[blybrook PE]

Unfortunately, It IS a wiring problem. Hopefully you have a Chilton or Haynes manual to refer to for the wiring diagram.

If the bulb is working elsewhere, then you've ruled out the bulb and are left only with the wiring. Since you've checked the fuses (not typically the problem if the other headlight is working) and it wasn't that, you've quickly ruled out the more common issues. Not knowing what type of vehicle it is, it is hard to determine if it is the wiring harness itself or the plug; but I'll give a few quick test methods to try. Some cars have plugs that wear out and won't have good contact with the bulb itself causing a faulty connection.

Typically, the headlight system is fed through the drivers light before going to the passenger, so if the passenger is working, then the wiring is good and I would look at the plug itself or the splice point where the passenger leaves the drivers connection within the wiring loom. There is sometimes a relay under the hood to boost the voltage to the light, but you can usually rule this out IF the other lights are working.

I would start by looking at the ground wire from the plug as this connection can go bad faster than others. If the ground is good, then get a 12v test light, ground the clip and turn on the lights. If the test light illuminates when pressed into the wire above the plug itself for the power side of things and not when pressed into the plug connection, you've found the problem and can replace the plug to get it operational again. If the light doesn't test, work your way UP the wire in the harness until you find the break; or until the light illuminates on the same wire; repair the wire to the plug and test again.

This is where I'd start. Good luck on the fix.

 

[roadwreck]

Thanks for the prompt reply guys. It's a 2003 scion tC (not a fancy luxury car). I've given up on the project for tonight (I've got to get ready for my wife's company Christmas party now) but I'll test some of this stuff out in the morning if I'm not that hung over.

 

[Flyer_PE]

First thing I would check is the ground connection on the bad light. Since the fuses aren't the problem and the other light works, you will likely have +12 getting to the bad light. The return path to ground would be my first suspect.

 

[pbrme]

Blybrook's diagnosis is spot on.

However, he didn't mention it, but I would also check the blinker fluid too. Wait come to think of it, scions don't use any.

that one never gets old.

I'm a big fan of Chilton's or Haynes if your going to do your own home auto repair.

Good luck

 

[blybrook PE]

I didn't want to mention blinker fluid since it was a headlight problem... Had he originally mentioned that it was a pre '85, then of COURSE there woulda been a blinker fluid mention if he was having blinker problems. Headlights didn't typically have the same blinker fluid circuitry; but sometimes you never know what the manufacturer did.

Haynes and Chilton are technically the same manual since they are written by the same group of people. One has a better electrical section though (IIRC it's Haynes). Some public libraries have the books in digital form that you can access from the internet should you not have the hard copy; you'd have to check with your local library though.

 

[Master slacker]

You've got a 2003 Scion? Audio suggestion: change out that t1806 or t1807 head unit for a t1814 or t1815.

I replaced my wife's 2002 Rav4 head unit with a t1814 and the sound quality is much better. Took all of 40 minutes to do it.

 

[Capt Worley PE]

At this rate I think I need to sell my cars and start riding the bus.

Well of course you should. That's what they do in Europe.

 

[DVINNY]

check the socket that the light bulb plugs into. they corrode fairly easily, and go bad.

I've had to cut their lead wire a couple inches back, crimp on the new socket, then shrick wrap (or electrical tape) the connections. Usually a few bucks for a new socket.