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School me on short-circuit detectors

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kornjulio

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My wife's minivan has heated outside rear view mirrors that are activated by the rear defrost switch on the dash. There's a short in the system somewhere and it keeps blowing the red 10A minifuse in the passenger side fuseblock.

I got no idea where the short is; and have not bothered trying to fix it for the obvious reason of not wanting to possibly tear the whole interior out to find it.

Now I'm reading about these detector gizzmos that's locate the short for me and save the grief holding me back.

So based on my issue, can anyone confirm the truth to this tool and secondly recommend me a unit???

BTW, I already have a Fluke 11 DMM; so all I want is something I can jam into the fuse, wave a magic wand, and pinpoint where the short is.....

Kevin
 
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WVU Tuba Dale

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Is it possible the mirror itself is shorting out? I have no idea about the short detector, but unplugging the mirrors, putting in a fuse, and doing a little process of elimination seems like a logical way to start. Chances are you will have to take apart the door panel(s) anyway, and they probably aren't too difficult to remove. Sorry for not being much help on the tool, but this is how I would approach this if I didn't have a magic wand. :beer:
 
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krusty the clown

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a short detector is simply a circuit breaker that you install in the place of the fuse and an inductive ammeter that you run along the wires to find where the wire no longer has a magnetic field. there is nothing majic about it.

use a circuit breaker and a wiring diagram
 
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K

kornjulio

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Sure, it could be the mirror. Could be the left one. Could be the right one. Might need to pull the door panel and it's 20 clips holding it on, might not. Might have to pull the whole friggin' instrument panel....

I know how to approach it with only simple tools, too. But the process of elimination approach usually results in a metric shitton of blown fuses littered across the garage and alot of time & effort. And if the short is in somewhere like the IP, I'm not gonna fix it and would rather not pull the rest of the van apart to figure that out....

Thanks, though.
 
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Mickey O

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krusty the clown said:
i'm just a mekanick not a english teacher........but thanks for pointing it out, you have saved merk the trouble of being the grammar police for today :rolleyes:
Click to expand...

Merk was busy and asked me to keep an eye on you guys.


Actually I was asking because some people say it that way, just curious.
 
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SouthCoastMudder

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Putting a bigger fuse in on a short could cause the wires to melt themselves, other wires in the same loom, or worse yet start a fire from the excessive heat of the short. Putting a bigger fuse in is a bigger no-no on a problem like that.
 
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caper

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Since it's also hooked into the rear defrost unplug the grid connector on the rear window.Nice and easy to access to eliminate one possible cause.
 
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Toolhorder

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I think you should just unplug the mirror and stick a new fuse in first and see if it blows. It's not that complicated. Most of those heaters have a little coil in the back and the coil shorts out. I'm sure that's what's wrong.
 
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K

kornjulio

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lynam said:
What don't you try a 20amp fuse in place of the 10a.
Click to expand...
Because I'm not ready to burn the van to the ground just yet. But when I am, I'll keep that in mind :thumbup:

caper said:
Since it's also hooked into the rear defrost unplug the grid connector on the rear window.Nice and easy to access to eliminate one possible cause.
Click to expand...
Good idea, but I've already ruled that out. When the fuse pops, the defroster lamp stays on & the backlite gets warm. So however the circuit is designed, the rear glass is independent of the heated mirrors after the switch at some point. Makes sense, too; since the heated mirror fuse is only 10A....I'm sure the backlite draws more than that...

krusty the clown said:
wasn't your question answered?
Click to expand...
Oh yeah, I'm gettin' lots of questions answered....
 
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Mr.Nutcase

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lynam said:
LOL.. a 20 amp fuse wont cause any fires..
Click to expand...

You are wrong!!!!!!!!!
Do that, It will have problems!
Stick to what the manufactor says!
If dodge thought it was ok for 20 amp fuse, it would have from factory,.
there is a reason why it has 10 amp fuse.
Just leave the work for a pro...
 
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Dust

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Santa Ana, CA
Check the wiring that goes between the body and the door. I get broken wires in there all the time. Usually causes an open, but sometimes the broken wire will rub the body and short out.
 
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M900

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lynam said:
It wont burn the hole van down to the ground.
Click to expand...

Youre right, it may just burn half of the van down...if the fire department gets there in time.:lol_hitti

Why dont you go replace all the 10A fuses in your car with 20A fuses?
 
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Toolhorder

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For everyone's info,

Fuses are designed to
handle more current than they’re rated for. To
illustrate: a fuse can handle 110% of its rated
current for at least 4 hours, 135% of its rated
current for up to 30 minutes, and 200% of its
rated current for up to 5 seconds.

I doubt the van would burn down but it's always a possibility. The method suggested is poor at best to find a short.
 
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lynam

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But?! if the fuse blows you know for sure its a short? im i wrong? or are we gonna have to call the fire department?
 
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ossaguy

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I remember reading an article in a Big Twin magazine of a cheap tester made by taking a common 12v turn signal flasher,and put short wires on it with alligator clips,and hook that into where the fuse goes into.So it wont blow,it will just flash,as it gets hot,then cools,hot,cools..etc.Then trace the suspected wirng path with a common small compass,and where the needle swings wildly,is where the short will be.

Some day I gotta try it.I have set aside a compass,just need to pick up a flasher next time I'm at an auto parts store.

Anybody else use this method?

Steve
 
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Roy 04 GTO

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krusty the clown

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ossaguy said:
I remember reading an article in a Big Twin magazine of a cheap tester made by taking a common 12v turn signal flasher,and put short wires on it with alligator clips,and hook that into where the fuse goes into.So it wont blow,it will just flash,as it gets hot,then cools,hot,cools..etc.Then trace the suspected wirng path with a common small compass,and where the needle swings wildly,is where the short will be.

Some day I gotta try it.I have set aside a compass,just need to pick up a flasher next time I'm at an auto parts store.

Anybody else use this method?

Steve
Click to expand...

a flasher is just a circuit breaker.......
 
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kornjulio

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kwhitelaw said:
year/make/model of the van?
Click to expand...
2000 Chevrolet Venture

As an update, I took a flyer and added this to an order I placed on ToolTopia last nite. We'll see how it goes!

31ot%2BpKRYzL._SL500_AA272_.jpg
 
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Q

quneur

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Two reasons I can think of why it's blowing fuses (my electronics is real rusty): 1. there is leaking current from another circuit. (ie. creating an inductance current.) 2. Somewhere on the circuit there's a component that's shorted, fused, etc. If it's no. 2, you are going to have to check each component on the circuit.

An open circuit will create an infinite resistor which none of the components will operate. But you have the opposite, a short (infinite capacitor - ground) where current is bypassing a component's (like a burn-out coil) resistance.

I think I got it right.
 
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quneur

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M900 said:
Should you EVER install a higher amp fuse?
Click to expand...

If there is another fuse within the circuit then its I say you can do it since it gonna blow that fuse or/and anything that's rated lower than that fuse. But putting a higher amp fuse would make it look like a jumper or plain wire. You know since it is blowing fuses, jumping it would cause the lowest rated component to blow first, theoretically.

I remember reading an article in a Big Twin magazine of a cheap tester made by taking a common 12v turn signal flasher,and put short wires on it with alligator clips,and hook that into where the fuse goes into.So it wont blow,it will just flash,as it gets hot,then cools,hot,cools..etc.Then trace the suspected wirng path with a common small compass,and where the needle swings wildly,is where the short will be.
Click to expand...

It would depend upon the ampere rating of the signal flasher. I would think if the amp rating on the flashing is higher than the circuit, the first flash then it would blow the circuit. As to the compass, I don't know. Compass are meant to point to magnetic north. Would the field strength be stronger?
 
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K

krusty the clown

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krusty the clown said:
a short detector is simply a circuit breaker that you install in the place of the fuse and an inductive ammeter that you run along the wires to find where the wire no longer has a magnetic field. there is nothing majic about it.

use a circuit breaker and a wiring diagram
Click to expand...

kornjulio said:
2000 Chevrolet Venture

As an update, I took a flyer and added this to an order I placed on ToolTopia last nite. We'll see how it goes!

31ot%2BpKRYzL._SL500_AA272_.jpg
Click to expand...

there you go........the tube with the wires coming out of the end is just a circuit breaker in a cardboard tube. and that is an inductive ammeter next to it.


the circuit breaker will help to keep from blowing many fuses while you find your short, but i'm guessing the ammeter will be useless (it will detect the magnetic field of any other wire in the harness. let me know if i'm right :bounce:
 
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caper

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Get youself a headlight bulp and attach a couple wires to it.Plug the wires in in place of the fuse.If there's a short the light should light up.Unplug connectors one by one until the light goes out to narrow down where the short is.It will not burn anything down because the light acts as a load to use the electricity,the short is just providing the ground.It's how we were taught in Ford training school.
 
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Toolhorder

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krusty the clown said:
there you go........the tube with the wires coming out of the end is just a circuit breaker in a cardboard tube. and that is an inductive ammeter next to it.


the circuit breaker will help to keep from blowing many fuses while you find your short, but i'm guessing the ammeter will be useless (it will detect the magnetic field of any other wire in the harness. let me know if i'm right :bounce:
Click to expand...

I've used that exact set before to diagnose shorts in the dealership. It's old school but works great. The Ammeter needle moves in the direction of the short as you move it across the circuit wire. The tube thingy you attach to the fuse holder just buzzes when the circuit shorts. It's a good tool.
 
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kwhitelaw

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unless the vehicle has been in an accident, or had some electrical work done prior (alarm, etc), I find it hard to believe a wire is shorted somewhere.. in over 10 years of auto work, I can remember 1 vehicle with a factory wire that shorted (interior wiring, not engine related) and that was an old mustang, in the drivers door boot..

on a 2000MY vehicle, im skeptical its a wire issue. I'd be more inclined to think its in the mirror itself. a simple test would be pulling the passenger door off, unplug the mirror, and replace the fuse. ten, move to the drivers mirror.

shouldnt cost you more than a handful of fuses..next time you are at the junkyard, pull a bunch out of some junkers and you'll be good for the future.
 
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