How to tell if a fuse is broken

[kcokla]

as titled.


thanks in advanced:)

[Frankie]

You get a test light like this
http://www.2carpros.com/dia/images/test_light.jpg
Than you put the metal tip on the top of the fuse metal on metal and if its broken it will lght up if its good it will light up

Cheers

[CRXer]

have a look at the curve bit of metal in the centre,if its broken,its blown.
have a look & compare it to another known good fuse,u will see the difference.

or put a multimeter across the fuse in place & ignition turned on,if it reads 12V,its blown...
if it reads 0V,its ok.

[kcokla]

thanks! understood!

[redefine]

have a look at the curve bit of metal in the centre,if its broken,its blown.
have a look & compare it to another known good fuse,u will see the difference.

or put a multimeter across the fuse in place & ignition turned on,if it reads 12V,its blown...
if it reads 0V,its ok.

:thumbsup: for the curvy bit, mine usually blow near the open end.

but if you have a multimeter, why use voltage?? chuck it on the resistance setting, and if you get inf, or OL or something its blown, if you get near 0 its still good

[CRXer]

but if you have a multimeter, why use voltage?? chuck it on the resistance setting, and if you get inf, or OL or something its blown, if you get near 0 its still good

save pulling the fuse out

[whiteballade]

You get a test light like this
http://www.2carpros.com/dia/images/test_light.jpg
Than you put the metal tip on the top of the fuse metal on metal and if its broken it will lght up if its good it will light up

Cheers

haha lol so how do you know?

[tseesinngwailo]

whats wrong with your car? if something is not working, put another fuse in, if it blows or whatever is not working is still not working, then trace out the wiring, if you need a diagram, PM me

Cheers

Chris

[bennjamin]

pretty sure he learnt first hand the fuse was not broken.

Something simply wasnt plugged in rofl.

Oh well. You learn !

[DLO01]

or put a multimeter across the fuse in place & ignition turned on,if it reads 12V,its blown...
if it reads 0V,its ok.

Thats not right Crxer, its the other way around. If the fuse is fine you'll read 12v, if its blown 0v. All paralel ccts will read 12v and thats effectivly what your doing with the multimeter. The meter on voltage does not complete the circuit with a blown fuse either because of resistance in the meter. If on current however it will complete the circuit with a blown fuse.

[kcokla]

pretty sure he learnt first hand the fuse was not broken.

Something simply wasnt plugged in rofl.

Oh well. You learn !



LOL, yes, ben helped me fix it as usual,

but thanks to all the useful information that was provided by everyone who contributed!:thumbsup:

[CRXer]

Thats not right Crxer, its the other way around. If the fuse is fine you'll read 12v, if its blown 0v. All paralel ccts will read 12v and thats effectivly what your doing with the multimeter. The meter on voltage does not complete the circuit with a blown fuse either because of resistance in the meter. If on current however it will complete the circuit with a blown fuse.

try it deano,

a good non-blown fuse has negligible resistance across it,
so if u have 12V on the line side of the fuse there is virtually zero voltage drop across the fuse element to the load side of the fuse,ie no potential difference= 0V.
more simply,both pins of the fuse exist at 12V,ie uve made a parallel circuit off 12V both sides.

a blown fuse has massive resistance across it(air gap),
u got 12V on line side of fuse & a circuit connecting to ground on the load side of fuse(assuming u have circuit switched on of course),
ie a potential difference of 12V across the blown fuse, minus what ever voltage drop across the load in the circuit is(most circuits will give close to a 12V reading anyway,its just mainly electronic gear that will give a lower reading).
more simply,one pin exists at 12V,the other pin exists at or close to 0V.

voltmeters do have a very high resistance,hence the ability to measure close to full voltage drop across whatever your measuring without adding its own value of drop.

[DLO01]

Sorry Crxer, your right man. I am a doushbag. :thumbdwn:

I like testing with one lead to the chassis and check points allong the cct. So on the +ve side of fuse you'll get 12v and on the -ve side if you get 12v the fuse is fine, if its 0v its blown.

[BI85LL]

http://upload.wikimedia.org/wikipedia/commons/thumb/6/6d/Car_fuses.jpg/800px-Car_fuses.jpg
^^^^^^ Good Fuse
http://farm2.static.flickr.com/1217/1243313900_6e8fae2f5a.jpg?v=0
^^^^^^Blown Fuse

[CRXer]

Sorry Crxer, your right man. I am a doushbag. :thumbdwn:

I like testing with one lead to the chassis and check points allong the cct. So on the +ve side of fuse you'll get 12v and on the -ve side if you get 12v the fuse is fine, if its 0v its blown.

dont worry deano,its easy to brush over what i typed & get confused with the concept,i knew someone would pick me up on it.

your method is prob an easier one to to try make people understand when they are asking about testing blown fuses,but the prob i always find is,i feel like always asking,"did u have a good ground connection when testing to make sure?".
Then u have to go on to describing how to establish u have a good ground reference for testing,it gets rather labourious.....considering nearly everything around the underdash fusebox is either screwed into plastic or painted,etc.
It just seems easier sometimes to tell people to hold a test probe on each fuse pin.

If your testing underdash fuses or whatever,a good easily accessible ground point is the ignition key or barrel.just clip your alligator clip onto the key or poke the probe into the barrel(key out),frees up one of your hands.

just dont make the mistake of testing only one side of all the fuse pins,i seen someone do it once & about to start pulling apart the car,they arent all necessarily live on the top or bottom/left or right,the logic & rules arent as strick when dealing with as little as 12V,peoples lives arent exactly at stake.....

we really need a diy on simple fuse testing(nice pic BI85LL),wouldve saved a lot of typing over the years,lol..........