12v Short in car wiring.

[AndrewG]

Hi, first post so be gentle!!

I have had a bit of an issue with my car recently.
I have a 2008 Honda Accord and had to MOT the car a week or so ago. On my pre-checks I noticed that the rear fog was not working. Bulb had blown so changed that but still didn't work so checked the fuse and found it was missing??? - now I bought this car exactly a year ago with 12 months MOT so should have been there??
Anyway, didn't have the 7.5a mini fuse spare so just for the MOT, I stuck a 15a fuse in and bought a pack of spare fuses on the way back home.
When I got back, just as I was about to turn the engine off, I noticed the rear fog was still turned on (dash light) but the bulb was not??. I checked the bulb again but it was ok and whilst I was messing with putting the bulb back in it come back on and then went off again??. I went to check the fuse again but noticed a bit of smoke coming from under the dash. I quickly turned off the ignition and disconnected the battery.
Once everything had cleared!!, the damage appears to be to the internal fusebox (MICU) and to one of the connectors which has got so hot it has melted into the socket on the fuse box. The wiring to that connector is also in a real bad way (see pics) and I guess my question to you is:

With the damage to the loom that can be seen, does anyone think there could be further damage unseen within the loom.?? The reason I ask is that one of the wires has completely burnt through so I'm hoping the short was localised in that area.

I am also hoping that the wire that has burnt out is the circuit that has the short.
I doubt that I'm insured for this so will have to sort this out myself.

What do people think??

 

[Guest111]

there could be and indeed probably will be damage further on down the loom,unfortunately my friend you have just learned a rather expensive lesson,while replacing a fuse with one of a lower value rarely leads to damage,replacing it with a higher one almost always does.

 

[AndrewG]

unfortunately my friend you have just learned a rather expensive lesson,while replacing a fuse with one of a lower value rarely leads to damage,replacing it with a higher one almost always does.

Yes, I know this and had I known there was an issue I wouldn't have done it :sad:

 

[Geordie Spark]

So you replaced a fuse with one of a "higher value" 100% higher value in fact and wonder why the loom went up in flames?

Well I think you have been a very silly boy!!

There now - that's me being "gentle" with you as requested! :yes:

 

[UNG]

Looks like more than one cable shorted there and probably originally more faults than just the rear fog light. Looks to me like you have a major earth fault on the vehicle

Best way to repair that would be a replacement loom from a scrap vehicle

 

[AndrewG]

Yes, I know I put in the wrong fuse and I've admitted to it but I was not to know that there was an issue. This is something I don't normally do and it's not like back in the old days when people used to wrap cigarette foil around a glass fuse!!. If there was no issue, the car would still be ok!
Sorry, telling me that I had used the wrong fuse does not answer my question.

I was wondering if the wire that has burnt out is the culprit (and I'm only assuming here) of the short, it would have lit up like a bulb and the heat generated has caused the damage to all the others whilst tightly bound within the loom.
I would have assumed (sorry to assume again but I'm not a qualified sparky) that the short would have gone to its perceived weakest point (like a bulb) and that's why it burnt out where it did. Would/could it have done the same damage elsewhere at the same time??

 

[Marvo]

Best way to repair that would be a replacement loom from a scrap vehicle

What he said ^^^

Yes there's a very high likelihood of loom damage elsewhere along its length. In theory if there's a short circuit the wiring involved will heat up fairly evenly along it's entire length. Looking at the damage in the area where it's exposed in the photo I'd say a replacement loom is your best option. Try to find one from a similar car, same model, same year and hopefully the colours will all match up.

 

[UNG]

Yes, I know I put in the wrong fuse and I've admitted to it but I was not to know that there was an issue. This is something I don't normally do and it's not like back in the old days when people used to wrap cigarette foil around a glass fuse!!. If there was no issue, the car would still be ok!
Sorry, telling me that I had used the wrong fuse does not answer my question.

Back in the old days vehicles were a totally different beast to today's vehicles where so much is electrical / electronic driven with multiple earthing points throughout the vehicle it only takes one or two of these points to fail and the circuit will find any earth point it can with what can be damaging consequences as you have found out

I was wondering if the wire that has burnt out is the culprit (and I'm only assuming here) of the short, it would have lit up like a bulb and the heat generated has caused the damage to all the others whilst tightly bound within the loom.
I would have assumed (sorry to assume again but I'm not a qualified sparky) that the short would have gone to its perceived weakest point (like a bulb) and that's why it burnt out where it did. Would/could it have done the same damage elsewhere at the same time??

It is difficult to assume anything without getting a meter on it to prove it out

 

[PEG]

Hi dude,how long was it steaming? And,with your bigger fuse removed,was it still shorting,ignition on/off? The problem you will have (or anyone else who gets involved) is exposing the damaged sections of loom,and separating them,to discover if there is any other damage. I have had this on very large items of plant,where days and days can be soaked up,finding and exposing damaged sections in bunched multi-cores in the the hundreds :icon12: A fuse box,and a section of loom would be a starter,but in all honesty,unless you have some experience of this,the removing of trim and components,will vex a sane man.I suggest you start at the source of the possible short (fog lamp unit) and work forwards.Good hunting :conehead:

 

[Geordie Spark]

Hi dude,how long was it steaming? And,with your bigger fuse removed,was it still shorting,ignition on/off? The problem you will have (or anyone else who gets involved) is exposing the damaged sections of loom,and separating them,to discover if there is any other damage. I have had this on very large items of plant,where days and days can be soaked up,finding and exposing damaged sections in bunched multi-cores in the the hundreds :icon12: A fuse box,and a section of loom would be a starter,but in all honesty,unless you have some experience of this,the removing of trim and components,will vex a sane man.I suggest you start at the source of the possible short (fog lamp unit) and work forwards.Good hunting :conehead:

"will vex a sane man" ... WOW!! I'm impressed, truly I am!!

What a wonderful turn of phrase that is ..... it's just ..... sublime!! :biggrin5:

 

[PEG]

"will vex a sane man" ... WOW!! I'm impressed, truly I am!!

What a wonderful turn of phrase that is ..... it's just ..... sublime!! :biggrin5:

Thanks,fella,now and again the influence from my English language/literature expert mother,out-performs that of my Gypsy/Showmen/Working-class friends...now and again...:icon12: