2001 Corolla, Fog Lights Always On
July 24, 2009 9:53 PM   Subscribe

My 2001 Toyota Corolla has spontaneously developed a problem: the front and rear fog lights never turn off, even when the key is out of the ignition. A good mechanic was recommended to me, but he won't be able to see me for several weeks. He warned me to expect to spend $200 minimum. Is there anything I can do in the meantime to try to solve this myself?

This is, naturally, a totally awful time for this to happen. This all began yesterday, with no precipitating incident.

My car simultaneously began exhibiting the following symptoms, which I'd never seen before:

1) Although my car normally has daytime running lights, my headlights stopped turning on automatically, both day and night. They do turn on normally when I engage them manually. My high beams also engage and disengage normally.
2) While the car is on, while the lights are off, the high beam indicator on my dashboard is blinking constantly, at roughly one second intervals.
3) When the door is open, the car's warning sound / idiot noise is emitted constantly (as if I'd left the lights manually turned on or the key in the ignition, but neither is the case)

Google gave me this, but in my case pulling the high beam switch does not temporarily solve the problem. I don't have a security system or anything unusual installed. I've tried pulling each of the smaller fuses in each of the obvious fuseboxes under the hood, and none extinguished the lights.

When making the appointment with the mechanic, I asked if there were a way to keep this from running down my battery. He said I could disconnect the battery lead while the car was off, but warned this would "wreak havoc" with my car's onboard computer.

The guy at the shop also told me to be prepared to spend at least $200 to resolve this. What little I can glean from Google seems to imply as high as $750 for similar problems.

Is there anything I can do to mitigate the problem myself? The solution doesn't have to be elegant or flawless, just get the car back to a state where I can drive it at night and it doesn't murder my battery. Any, any insight is appreciated.

Thanks in advance
posted by churl to Travel & Transportation (21 answers total) 2 users marked this as a favorite
Best answer: A bit of a pain in the ass (and definitely an inelegant, temporary solution), but you could look in your owner's manual to determine which fuse the fog lights are on, and remove the fuse when you park your car. Just remember to put it back before you drive.
posted by dersins at 9:59 PM on July 24, 2009

That's not a good mechanic.
posted by 517 at 10:05 PM on July 24, 2009 [2 favorites]

Alternatively (and even more annoyingly), you could remove the positive terminal on your battery when you turn off your car. I once had a p.i.t.a. voltage drain that we couldn't locate and that was the quick and dirty fix for a short period of time to save my battery.

Good luck!
posted by ThaBombShelterSmith at 10:06 PM on July 24, 2009

Electrical problems are a bitch to track down for sure. At least it's in the semi restricted area of "lighting". As much as I hate to say it, I'd take it to a Toyota dealer. They have likely dealt with this several times before, based on the google hits your problem suggests. A normal mechanic could spend days tracking down the problem, which is probably where his pricey estimate came from.
posted by sanka at 10:18 PM on July 24, 2009

You could also just take the bulbs for your fog lights out, or if they're on a separate fuse just take the fuse out.
posted by delmoi at 10:27 PM on July 24, 2009

Best answer: Disconnecting the battery won't wreak nearly as much havoc as having a completely drained battery, and doing this multiple times. You should definitely find the right fuse or disconnect the battery when the car is not in use, until you find the correct solution. The fuse may be in the car by the driver's left knee, at least, that's where many cars have them. (You noted that you searched the engine bay fuses already. Obviously there is a fuse for that circuit, you just haven't found it yet.)

I believe his concern about the computer is that most fuel-injected vehicles adapt to driving conditions over time, and disconnecting the battery forces the computer to start this process from scratch. This means the car may run a little rich (using slightly more fuel than usual) while it accumulates data and adapts to your specific driving conditions. I don't think it's anything to worry about, and it's better to do this than kill your battery the hard way.
posted by knave at 10:30 PM on July 24, 2009

Seconding that pulling the ground off your battery is just going to cause the computer to have to remap; the care will run slightly sub-par for a while, but the alternative (a dead battery) will just put you in that position anyway, plus you'll have a battery that's been completely drained.
posted by davejay at 10:56 PM on July 24, 2009

You could also just take the bulbs for your fog lights out

No need to do that, just unplug them. That could actually solve your problem semi-permanently, if that's the only battery drain you have.
posted by @troy at 11:48 PM on July 24, 2009

I'd see an auto electrician, not a mechanic.
posted by onya at 12:14 AM on July 25, 2009

One thing fiddling with your battery connections will do, is give you the opportunity to thoroughly inspect and clean them. I've seen corroded battery terminals cause flaky electrical problems, like you report in your second and third trouble points. Older batteries can develop tiny case cracks around the battery terminals, too, allow acid fumes and discharge gases to evaporate directly around the terminals, exacerbating terminal corrosion, too.

Whenever you are trying to troubleshoot a car electrical problem, it pays to start by cleaning both battery terminals, as well as physically inspecting, cleaning and testing the battery. You can do everything but testing the battery yourself, and you can take the car to most auto parts stores (but, for sure, Autozone) for a free charging system test and analysis, that will tell you whether your battery and alternator are good.

With all that out of the way (for no money, probably), you'll be in a position to continue looking for random wiring shorts, on the ground side of your lights, which could be turning them on, if you are still having lighting problems.
posted by paulsc at 2:53 AM on July 25, 2009

I'd see an auto electrician, not a mechanic.

Seconded. The last time I had random behaviour that affected multiple electrical systems, the problem was corrosion in a big connector sitting between two big cable bundles. My ordinary garage was baffled, but it took an electrician 20 minutes to identify and fix the problem, without having to replace anything.

(Well, the last time I had random behaviour was in a rental earlier this month, when they'd forgot to put on the oil cap after a service. The engine computer couldn't make sense of what the sensors kept telling it, so it randomly switched over to an 1200 rpm max emergency mode... Took a reboot to make that engine run properly again.)
posted by effbot at 4:06 AM on July 25, 2009

If you are at all electrically inclined, now is a good time to invest in a Hayne's manual: they usually include wiring diagrams that can help you figure things out.

Also, like the other people above said, an electrician is an entirely different beast from a mechanic: car electrical systems are even flakier than computers, it pays to go to someone with a strong mojo.
posted by Dr Dracator at 4:30 AM on July 25, 2009

Install a battery kill switch. Easy and cheap.
posted by saladin at 6:54 AM on July 25, 2009

Just undo the connectors to these lamps.
posted by A189Nut at 7:51 AM on July 25, 2009

I have a 91 Toyota Celica that did the exact same thing and I sourced it to a faulty turn signal assembly. But the thing about electrical problems is that a short could occur anywhere to mess things up. It was obvious for me because whenever I used the signal knob to turn left, if I turned it TOO left my car would make a sound like a buzzer, and you could hear the leak a bit in a quiet area if you listened carefully.

My solution was to take out the battery. I suggest you repair it soon because the problem spread to my headlights intermittently while I slacked off on the repair.

The replacement of the turn assembly would have been about $80 for the signal and an hour of labour in your area. But if they need to do some diagnosis to find the source of the short, that could jack up the price easy.
posted by ajackson at 7:59 AM on July 25, 2009

I think this is an L1, L2 or similar lighting relay failure (at least that's how it is with Lexus which are Toyota). I had to replace the L2 relay on my Lexus and it was, alas, about $1100 at an independent mechanic. I do think that it was extra expensive on my car because of extensive labor involving the dismantling of a lot of the grille and front end pieces to gain access to the relay. On the Corolla, I *think* the foglight relay is under the passenger side kick panel.

You may be able to simply remove the relay as it is a socketed component. I would try to ask a Toyota dealership service person before trying this and I'd disconnect the battery before trying it.
posted by bz at 11:08 AM on July 25, 2009

Response by poster: Thank you all so much for your help here.

I should have been clearer that the "mechanic" I spoke with at the shop was not the actual wrench-turner -- just the guy at the counter, and the numbers he threw out were just speculation. The shop does have an auto electrician, who can see my car 2-3 weeks from now when his schedule permits.

For now I've just pulled the battery. I guess after sweating over this for the last couple of days, the main issue for me is not knowing how much it will ultimately cost. I am prepared to spend a few hundred dollars, but somewhere loosely around $800+ it becomes cost-prohibitive for me to deal with right now. And it sounds like turning the car over to the shop means -- basically -- agreeing to pay whatever it ultimately costs. I've had this car for years and it has run like a dream, but has already abruptly cost me a lot of money in the last few months (unrelated non-electrical issues) and it kinda feels like the honeymoon is over.

My sense of urgency is probably working against me. From the advice here it sounds like I should make another search for the appropriate fuse, and failing that, disconnect the lights themselves. If that works, it will solve the problem adequately for now, at least until I'm more financially prepared to dive into it with an auto electrician. I'll also try to inspect the battery connections and other wiring, and see if I can find the 'relay'.

If it doesn't, maybe it's fate. My next question might be about how to shop for a bike.

Thanks again, I'll report back with results. This is all much, much appreciated.
posted by churl at 1:15 PM on July 26, 2009

Do you have an owner's manual? My Saabaru has a switch on the top of the steering column that turns on the parking lights and disables the daytime running lights. I accidentally hit it one day while cleaning the interior of my car and just about had a cow until I figured it out (by Googling "wrx parking lights always on", in fact). Poke around and look for little switches that you don't often press, and read every page of the manual.
posted by TheNewWazoo at 10:07 AM on July 27, 2009

Response by poster: So in addition to the three I found in the engine compartment, there is indeed a fourth fuse box exactly where knave guessed it would be: there's a small pull-out tray near the driver's left knee whose utility is hard to guess, until you pry the entire damn thing out and discover the fuses concealed behind it. The reverse side of the tray has the legend for the fuses. Pulling the "FOG" fuse did not alleviate my problem, but pulling the "TAIL" fuse did. The fog lights extinguish, and the 'idiot noise', which was sounding when the door was open, ceased.

The headlights still don't turn on automatically like they used to, day or night, but manually engaging the headlights (and high beams) still works.

I tried my best to inspect all the electrical contact points I could find in the engine compartment, but saw nothing that seemed unusual. The battery is less than a year old and there is no observable corrosion at the contacts or anywhere else I could see.

Because of the advice here, and especially because of how unpredictable the final price of fixing this might be (ajackson having a similar problem fixed for $80-ish, while bz had a similar problem fixed for $1100 -- my condolences), I've decided this is not the problem I want to use to 'test-drive' a new mechanic. Finding and pulling the fuse has alleviated the problem enough that I can wait on the repair a while -- until my next chance to see my old, ultra-trustworthy mechanic in my old hometown, and see what he says.

Every single answer here was helpful. Thanks again everyone, I really feel like you've helped me dodge a bullet.
posted by churl at 1:20 PM on July 27, 2009

Best answer: Nota bene: pulling the TAIL fuse also likely disabled your brake lights. Be doubly sure that's not the case (check them with headlights both off and on) before driving anywhere.
posted by TheNewWazoo at 3:53 PM on July 27, 2009

Response by poster: Jesus, why didn't I think of that? I just checked and it indeed disables my main brake lights (the third brake light in the rear windshield still illuminates, though). I'll replace the fuse whenever I drive. Thanks for catching that, you're a lifesaver.
posted by churl at 6:26 PM on July 27, 2009

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