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View Full Version : Foglight burn out the fuse. WHY???


SickFinga
06-03-2004, 12:38 AM
When I turn on my foglight, my fuse burns out right away.
I though it was the bulbs, i changed them - same thing.

Then I disconnected left fog housing, right one worked
connected left one, disconnected right one - worked

but when they are both on, fuse blows.

Any idea why???

328is_Perf
06-03-2004, 12:42 AM
i know this might sound stupid... but do you have the fuse with the right amps in?

Justin e36
06-03-2004, 01:22 AM
... I had the same problem. But it always blew no matter if it was left or right.. turned out to be corroded wires touching the chassis of the car. I rewired them.. (cost around $4 for the connectors and everything)... and no problems since.

SickFinga
06-03-2004, 02:57 AM
any ideas where i should look??

Quack
06-03-2004, 04:55 AM
look at the wires going into the foglight assembly, those wires are exposed never completely sealed, also check the connectors

Justin e36
06-03-2004, 03:40 PM
yep.. bump quack.

try actually pulling the foglight wires and plug out the top of the engine.. (reach down, and pull it up.).. you should be able to examine the wires easily like this, and individually wrap them in electrical tape before trying again...

Betray
06-06-2004, 10:44 PM
bump

MP328
06-07-2004, 04:00 AM
did it start happening just for no reason or did u just change the bulbs?

whats the bulb wattage??

i put once 100W in my fogs and it didnt last a whole night it burned the bulb and the fuse

Betray
06-07-2004, 08:27 AM
just happened for no reason

MarkD
06-07-2004, 04:24 PM
Originally posted by SickFinga
When I turn on my foglight, my fuse burns out right away.
I though it was the bulbs, i changed them - same thing.

Then I disconnected left fog housing, right one worked
connected left one, disconnected right one - worked

but when they are both on, fuse blows.

Any idea why???

You need a bigger fuse. What amperage is the one that is blowing? You will have to increse the capacity by the extra current used by the fog lamps.
Lets's say you have lamps that are 50W each. That is 100W total extra power. Using the formula P = IE, or I = P/I, this would be 100 W / 13.8 V = 7.25 A

So if you have a 15 amp fuse right now, you should change it to the closest size above 15 + 7.25 = 22.25 A which is probably a 25A fuse.

It would be better to run a separate circuit for just the fog lamps with it's own fuse. Then an 8 or 10 amp fuse just for the fogs should be fine.

MarkD

SickFinga
06-08-2004, 06:46 AM
MarkD, I don't wanna run anything higher them OEM recommended. It just started happening for no reason whatsoever. The fuse that is burning out is 5A, and it is supposed to be 5A.

MarkD
06-08-2004, 09:55 AM
Originally posted by SickFinga
MarkD, I don't wanna run anything higher them OEM recommended. It just started happening for no reason whatsoever. The fuse that is burning out is 5A, and it is supposed to be 5A.

Then I misunderstood. I thought you just added some new fog lamps and then started having a problem.

But a 5A fues seems low for that application. How many watts are these fogs? If there is nothing else on the same circuit, a 5A fuse is only good for two lamps that are about 25W each.

MarkD

Justin e36
06-08-2004, 03:21 PM
Bigger fuse?... not a good idea.

Fuse is rated depending on the guage wire for the foglights... the fuse is designed to blow before the wire burns out or gets too hot / causes a fire.

higher amp fuse will not burn out.. but the wires will get hot and eventually burn out / cause a fire instead.

BMVV
06-09-2004, 12:43 AM
Fuses offer short circuit protection and over current protection. If this happened out of the blue, you must have a short to ground ( the frame or body) so look for bare copper somewhere.