Replacing a halogen with LED bulb?

I hope you are not one of those people who insist on using their fog lights all the time. They can be blinding to oncoming traffic and completely unnecessary in normal driving conditions. Fog lights should only be used in ... wait for it ... fog!

I know that doesn't answer your question, but if you used the lights only when needed, the regular incandescent bulbs would last a lot longer.

_Properly-aimed_ fog lights should never blind anybody unless they are crawling along the pavement. The idea of the lights is that they are to be aimed low and have virtually no upward scatter. If they are doing anything else then they are not really fog lights.

Fog lights are really an antiquated legacy term now, they are now more properly referred to as "driving lights". If they were still really fog lights then they would be tinted yellow, but most of them are clear colored now. They are just designed to fill out the blindspots not covered by the headlights, immediately to the front and to the side of the car. That's why they're mounted so low. And also because they are so low on the ground, they shouldn't really blind oncoming traffic as it's aimed too low for oncoming traffic to be directly affected. However, running high-beams while in oncoming traffic will definitely blind oncoming traffic! The high-beams are aimed as far forward as possible, so oncoming traffic will definitely be affected by that.

Doesn't help, I've seen these go dead even with little or no utilization. That's why I'm wondering if the LEDs will do better down there?

Yousuf Khan

It would seem then, from my own experience, that very few fog lights are properly aimed. BTW, a number of respected automotive writers hold the same view regarding fog lights, to whit: they are for use in fog and are not intended to be used as regular driving lights.

OK, so how is a fog light different from a "regular" headlight?

A traditional fog light has its optics designed such that the light output has a near-total cutoff in the upward direction -- its beam is flat and wide. They are mounted as low as practicable on the vehicle; in the olden days of Lucas 200,000 candlepower (such were the units in the day) lights they were invariably mounted below the front bumper (which in the day were actual chromium-plated steel thingies). Thus designed and mounted they did not cause scattering of light from the fog particles and could not blind oncoming traffic.

Back in the late 60s I had a pair of these Lucas fog lights below the bumper and a pair of Lucas 'driving' lights above along with aftermarket (illegal in the USA) 250,000cp headlights on my pseudo-rally car. All were independently switched and driving in heavy fog in the eastern mountains with just the fog lights, no headlights, was a revelation. Headlights, even dipped, and fog are a killer.

OK, so that was just rambling, but I am getting old so give me a break...

I had aftermarket fog lights on a car in New Jersey, where the law required that the fog lights not come on unless the headlights were also on, which rendered the fog lights useless. The rationale for the requirement was otherwise criminals could run with only fog lights on, leaving the tail and license plate lights off.

It used to be that lots of people around here (Virginia suburbs of DC) always ran with fog lights on. This was at a time when few cars other than BMWs came with foglights standard. I asked the driver of one of them why she always ran with foglights on and she said the dealer told her to do that.

This thread brings to my attention that I no longer notice cars running with foglights on any more. I guess foglights have become common so they no longer announce "Hey look at me I'm driving a BMW."

Yeah. I think that particular requirement was/is a part of national code but, being 22 years old and enjoying my first 'good' car, I didn't pay a lot of attention to that -- I had installed heavy-duty relays feeding each set of lights directly from the battery terminals controlled by separate switches on the dash. By an oversight by the car's maker it was also possible to turn on both the high and low beams of the headlights simultaneously by using the flash stalk to my admittedly-illegal headlights so I could put out enough light to see for miles and miles if I chose to. Sadly, the puny alternator in the car couldn't keep up with the load and the battery had to make up the deficit so I didn't do that often. Sure seemed exhilarating at the time though...

Sounds about right for New Jersey- limiting/punishing the law abiding many for the (potential) misdeeds of a few...

Thanks, and no worries, I'm probably older than you are!

I had an early 70's BMW 2002 which the previous owner had mounted a pair of dinner-plate sized non street-legal Cibie babies that lit things up clear into the next county.

Yeah, my recollection of real fog lights too from back in the day. This is the closest image I can find from a modern car that is a real fog light.

Yousuf Khan

Okay, so here's an update. So I did end up buying the LED replacement bulbs. They looked somewhat bulkier than the original halogen bulbs, so I was worried whether it would fit through the socket at all! The bulbs arrived the next day from Amazon. I then had my mechanic try to replace the bulb, but it couldn't even fit through the opening! Damn! So I had to return the LED's back to Amazon. On a positive note, it's extremely easy to return things to Amazon, all I had to do was print up a return label which Amazon itself paid for, and then drop it off to the local post office.

On another note, the bulb that I thought had burned out, hadn't burned out at all, it was still functional! I have no idea why it's happening, but knocking on the exterior of the light housing brought the light back to life! This happened to this same fog light last year, and then it got fixed somehow and never happened again, until it happened again this year. It seems to happen during the winter mostly. I'm thinking that perhaps a short or a loose wire causes it? So I couldn't replace the bulbs with LED's, but the original lights are now working again!

Yousuf Khan

Ah yes. The BMW 2002. I lusted mightily for a 2002 Tii at the time. Couldn't afford it as I was in the USAF but that didn't stop me from driving by the dealership every now and then...

One of the jealous knuckleheads I worked with back then used to rag me- calling it the world's most expensive Fiat. I wouldn't give him the satisfaction at the time but I have to say, the body lines were similar to the then-current Fiat :-(

Sounds like the connector for the fog light isn't inside the engine compartment (as with the headlights) but perhaps inside a front bra or grill assembly, like in a bottom recess with the rear side exposed to road grime. If so, could be the connector is getting corroded. Remove and replace the connector a dozen times, or more, to scrape away the corrosion where the parts of the connectors contact the bulb's contacts. Then squeeze some dielectric grease into the connector or on the bulb's contact points to make it water and corrosion resistant. This is the same stuff used in many automotive connections, trailer hitch connectors, and inside the spark plug wire boots to prevent corrosion. Alternatively, you might something at the same auto parts store called bulb grease. Also, bulbs inserted dry can be a bitch to remove later.

Another possibility when rapping on a bulb and it comes back to life is that the filament inside has a flaky connection to the internal contacts. Remove the bulb with it still attached to the wiring harness connector and with the lights on. Shake hard the bulb. You want it to break under test rather than on some rainy cold and foggy night when you really need it. I carry extra headlight bulbs (mine are replaceable), taillight, and other bulbs in my toolbox that resides in my car so I have spares on hand when they go out (rather than one-eye driving at night or other drivers not sure that I hit my brakes or a turn signal not alerting other drivers of my intention).

Easier said than done. The Tribeca's foglight placement is probably one of the worst designs ever! Immediately behind the passenger-side foglight there is some sort of fluid container (I assume the radiator overflow), that makes putting anything bigger than child hands a near impossibility, let alone putting your head there so you can see what you're doing. Most of the time the only way to see what you're doing is to put a camera-phone in there, take some pictures, figure out where things fit, blindly fit them in, and hope everything worked out.

Also the car needs to be hoisted up on car lift to get these bulbs in or out.

The filament was fine. It looks like the problem lies with the wire that comes from the car and attaches to the bulb.

Yousuf Khan