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Why did my headlight socket catch fire?


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The title is the short and dirty version. My passenger headlight has been intermitten for a few weeks and about a week ago it cut out completely, I figured it had burned out so I did a quick check under the hood and the socket had fallen off of the headlight. I didn't really have a good look at it then (I was more worried about the cop) but it cut out again two days ago and so I figured the socket had just fallen off again, but... this time the socket had been burnt pretty badly, it appears that it was caused by the wire at the top of the socket (I haven't checked the diagram to see what wire this is yet (I'm assuming hot:-p) the socket itself is trashed so I was going to ghetto fab something until I can afford to fix it properly.

 

Thanks,

 

Bryce

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Most likely the socket was arcing internally. IIRC there are 3 wires, the top being hi beam right, lo beam(from the back of the bulb) left, ground. if it was intermittent, it was arcing inside the plug, creating heat. Eventually the plastic surrendered to the super hot arcs (think welding) The bulbs are supposed to fit pretty tight, if they don't eventually they'll do this.

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Most likely the socket was arcing internally. IIRC there are 3 wires, the top being hi beam right, lo beam(from the back of the bulb) left, ground. if it was intermittent, it was arcing inside the plug, creating heat. Eventually the plastic surrendered to the super hot arcs (think welding) The bulbs are supposed to fit pretty tight, if they don't eventually they'll do this.
Sounds good to me. I'll replace the socket eventually but for today at least I am going to replace the connectors, wrap them in some electrical tape, and call it fixed. (i'll keep an eye on it; scouts honor)

 

Thank you

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[...]My passenger headlight has been intermitten for a few weeks and about a week ago it cut out completely, I figured it had burned out so I did a quick check under the hood and the socket had fallen off of the headlight. I didn't really have a good look at it then (I was more worried about the cop) but it cut out again two days ago and so I figured the socket had just fallen off again, but... this time the socket had been burnt pretty badly, it appears that it was caused by the wire at the top of the socket (I haven't checked the diagram to see what wire this is yet (I'm assuming hot:-p) the socket itself is trashed so I was going to ghetto fab something until I can afford to fix it properly.

Heat is produced when electric current flows through a resistance. Corroded/loose connections tend to be resistive. The heat produced is proportional to the power dissipated, which can be calculated by multiplying the resistance times the square of the current going to the headlight. Since headlights draw several amps, it doesn't take much contact resistance in order to develop quite a bit of heat. It doesn't matter whether the poor connection is "hot" (battery plus) or ground, the heating effect only has to do with the magnitude of resistance and current.

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Subaru's headlight wiring is..not good to say the least. There's been far too many cases of headlight connectors and wires melting or catching fire :-\.

 

Unfortunately, it's hit or miss and usually the best way to fix it is to add in some extra relays to aid the system.

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hapened to me already b/c of a bad bulb i bought....went to the junkyard got the headlight socket, spliced it onto my car..then plugged it back in

 

two days later it melted again, so i figured it was the bulb; changed it and all has been well since

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Same here and on the passenger side too. I got a OEM socket from a guy on NASIOC. I spliced them together with a bit of extra lenght, I think that could be a part of the problem. It seemed like quite a strech to get the original socket on the bulb. So far so good, hope it works out for you, Tim

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My 2 cents, from Nissan experiance again.... We see this all the time (Same style bulbs and wiring on a lot of Nissans) Everything said about loose connections building heat is, of course, true. But where I see it happen ALL the time is aftermarket bulbs, usually the higher wattage babys...or the no-name cheapo ones from AutoZone, etc. (I know it sounds far-fetched, but I think those cheapy bulbs use lousy metals for the 'prongs' or something) I would stick with name brand bulbs, and if you want to run the brighter ones, I'd go with some heavy duty sockets and run relays. We stock the heavy duty sockets which come with larger gauge wire pigtails, and use them for all socket replacements.

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This is with straight (stock) 9003 bulbs I think... as replacements I did get hotter bulbs though (I haven't installed them yet) Today I got some replacement sockets at auto zone for $10 that say they are good for aftermarket bulbs (we'll see) I am going to install the sockets later tonight (I ghetto fabbed it for now) right now I have to go see if I can drive the car without blowing the engine. To be continued in another thread (maybe)...

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Since everyone is ***************ing, I might as well do to. I use headlights a lot, They shut with the engine so I keep them on. They are not as I have found, daylight running lights. After a few years, I went for inspection and the mechanic told me I needed a bulb, So no choice but to say OK. Two weeks later, The bulb went again, so this time, I bought one only to find out the mechanic didn't change the bulb, it was the connector. Got screwed ( I guess he did since he lost a customer for $14.00). Anyway. both connectors were fried from the heat. I called Subaru and was informed that I needed to replaced the entire assembly at a cost of approximately $400.00. The coglione on the Subaru parts department to quote me that price. So I did what McGuyver would have done, strip the wire, attach it to the bulb, and wrap it.

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Since everyone is ***************ing, I might as well do to. I use headlights a lot, They shut with the engine so I keep them on. They are not as I have found, daylight running lights. After a few years, I went for inspection and the mechanic told me I needed a bulb, So no choice but to say OK. Two weeks later, The bulb went again, so this time, I bought one only to find out the mechanic didn't change the bulb, it was the connector. Got screwed ( I guess he did since he lost a customer for $14.00). Anyway. both connectors were fried from the heat. I called Subaru and was informed that I needed to replaced the entire assembly at a cost of approximately $400.00. The coglione on the Subaru parts department to quote me that price. So I did what McGuyver would have done, strip the wire, attach it to the bulb, and wrap it.

 

 

haha...is it still like that?

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