Hello.
The car is a Xsara estate 1.6 Petrol, year 2000. After driving 1/2 an hour, with only A/C on (no lights, no electric windows in use etc.), heavy smoke started to rise from behind the rear seats and after stopping engine it stopped also. I checked and found out that 1 wire, from the central main pigtail wires leading to the back of the car, is responsible for the-almost-disaster. Probably the one that is in charge of the rear wiper, but I'm not quiet sure. My questions:
1. Way did the fuse not reacted and burnt, instead of this wire? What are the fuses for??
2. Any ideas why this happened? The wires are still original packed; they come from the left front side, go beneath driver's seat to the right side, upwards to estate small window on the right and then reach the back. As I mentioned, only A/C was in use and the car has only front outlets.
3. Why does this wire stop from heating itself again after this occasion? I measured 14 volts on the exposed wire with the engine on. I can now drive the car & the smoke stopped.
4. What should I look for in order to prevent such an occasion again, in the future?
Many thanks in advance!
Michael.
Wire burnt on Xsara – almost burning the whole car down;
Moderator: RichardW
first question is... was there a fuse for this item, and was it the correct fuse, go to the fusebox and check ALL (inside and out) the fuses carefully, check what items each fuse protect, and check especially what rating they are... someone might have put a big fuse where a small one is needed 'for a temporary solution', hence the burning
rear window demisters take quite some current, maybe the timer for it has broken and it didn't switch off automatically in good time, or it's stuck on (the light in the dash might also not be working) it won't burn the glass obviously, so the heat would travel down the wire and burn it (this is just a suggestion of course)
it could also be a sticky brake switch, check that they aren't on all the time.
if you can try to get a wiring diagram and follow the wire colour and see exactly what it should be powering, what switches and relays and where the feed is
i don't think the fact the AC was on had something to do with the burning wire
let us know what you get
rear window demisters take quite some current, maybe the timer for it has broken and it didn't switch off automatically in good time, or it's stuck on (the light in the dash might also not be working) it won't burn the glass obviously, so the heat would travel down the wire and burn it (this is just a suggestion of course)
it could also be a sticky brake switch, check that they aren't on all the time.
if you can try to get a wiring diagram and follow the wire colour and see exactly what it should be powering, what switches and relays and where the feed is
i don't think the fact the AC was on had something to do with the burning wire
let us know what you get
Car electrics are fun as all car electrics designers seem to have been brought up in the age of the horse and cart and seem to approach the subject with the knowledge needed to look after a horse.
What do I mean - well you've found lots of lovely fuses - but if you look at the diagram you'll find a number of circuits unprotected, for example on a BX and many others - the headlights (Safety my boy - dangerous if they all go out when you need them at night - so don't fuse them!)
If you're sensible when designing circuits you put the fuses at source - like your house wiring - incoming cable - company fuse, consumer unit with fuses, house electrics. Cars don't have them next to the battery - no they're scattered all over the place and are miles down the wire - so all the circuit ahead of the fuse is unprotected.
If you run an indicator light bulb for a few minutes the glass will get too hot to touch. Its consuming about 2 amps - so you will see that in car terms (where 20 amp circuits are common) there is potential for considerable heat generation without blowing a fuse. A dead short will blow a fuse quickly - a failed component or partial short will not and may produce loads of heat - which can cause fire.
Your problem is related to something wired through that part of the car which was live at the time. Rear wiper is unlikely as its on a switched feed and wasn't on at the time so its wire would have been dead. Same should go for most things - except the boot light but this wouldn't have switched off when you stopped as its generally live all the time.
I agree with deian. Brake lights would take about 4 amps and may not be fed from a cable of sufficient capacity for continuous application but I wouldn't have thought this unlikely as I've never heard of anyone getting smoke when sitting in traffic queues with their foot on the brake - and I'm sure someone has done it!
Many years ago I had a Renault 21 - on which the electric fan seemed noisy on its annual use (thing never really seemed to need it). One hot day I went to work and just as I was waiting to turn right smoke started coming up form behind the dashboard. It was still running so I went on and parked up well away from everyone and doused as much as I could see with water - and as all seemed well went and did my shift. At 6am I drove it home without trouble - and when I came to examine it I found the fan was on one enormous circuit protected by a 75 amp fuse - which of course is as good as useless!
Had an enjoyable afternoon in front of the TV dismantling the main loom and replacing damaged wires - re-assembled - and about a year later got round to fitting a properly wired fan with a relay and its own modest fuse.
Charred insulation will continue to do its job while its still there - but of course flexing may dislodge it and allow a short. My suggestion is that you trace the wiring back towards the battery and examine it thoroughly. Damage may stop where it joins a conductor of a heavier capacity. It is likely that the damage is confined to the faulty circuit - but adjoining wires may have heat damage which may need repair. These wires will however only be damaged where they are in contact with the faulty circuit - ie in the same loom.
What do I mean - well you've found lots of lovely fuses - but if you look at the diagram you'll find a number of circuits unprotected, for example on a BX and many others - the headlights (Safety my boy - dangerous if they all go out when you need them at night - so don't fuse them!)
If you're sensible when designing circuits you put the fuses at source - like your house wiring - incoming cable - company fuse, consumer unit with fuses, house electrics. Cars don't have them next to the battery - no they're scattered all over the place and are miles down the wire - so all the circuit ahead of the fuse is unprotected.
If you run an indicator light bulb for a few minutes the glass will get too hot to touch. Its consuming about 2 amps - so you will see that in car terms (where 20 amp circuits are common) there is potential for considerable heat generation without blowing a fuse. A dead short will blow a fuse quickly - a failed component or partial short will not and may produce loads of heat - which can cause fire.
Your problem is related to something wired through that part of the car which was live at the time. Rear wiper is unlikely as its on a switched feed and wasn't on at the time so its wire would have been dead. Same should go for most things - except the boot light but this wouldn't have switched off when you stopped as its generally live all the time.
I agree with deian. Brake lights would take about 4 amps and may not be fed from a cable of sufficient capacity for continuous application but I wouldn't have thought this unlikely as I've never heard of anyone getting smoke when sitting in traffic queues with their foot on the brake - and I'm sure someone has done it!
Many years ago I had a Renault 21 - on which the electric fan seemed noisy on its annual use (thing never really seemed to need it). One hot day I went to work and just as I was waiting to turn right smoke started coming up form behind the dashboard. It was still running so I went on and parked up well away from everyone and doused as much as I could see with water - and as all seemed well went and did my shift. At 6am I drove it home without trouble - and when I came to examine it I found the fan was on one enormous circuit protected by a 75 amp fuse - which of course is as good as useless!
Had an enjoyable afternoon in front of the TV dismantling the main loom and replacing damaged wires - re-assembled - and about a year later got round to fitting a properly wired fan with a relay and its own modest fuse.
Charred insulation will continue to do its job while its still there - but of course flexing may dislodge it and allow a short. My suggestion is that you trace the wiring back towards the battery and examine it thoroughly. Damage may stop where it joins a conductor of a heavier capacity. It is likely that the damage is confined to the faulty circuit - but adjoining wires may have heat damage which may need repair. These wires will however only be damaged where they are in contact with the faulty circuit - ie in the same loom.
jeremy
Thank you kindly for your quick reply.
I assume (logically) that there's a fuse for everything – correct me if I'm wrong – and that there might be a few users under one fuse. Could it be that a user is not equipped with a fuse? Anyway, I don't know if the rear wiper is the cause (it was not in use for the last 2 months) and the problem is that the owner's manual supplied with the car is not exact and probably refers to older models (my car is a 2000 production, has the older shape but is supplied with the AL4 auto transmission...) What do you mean by "the light in the dash"? Do you mean the one in the trunk? Well, I've noticed after the fire that it is on constantly with no apply to the doors situation, but I do not know if it was on all the time before. The car is in the garage now and I will inform you later what is going on.
Thanks again – Michael.
I assume (logically) that there's a fuse for everything – correct me if I'm wrong – and that there might be a few users under one fuse. Could it be that a user is not equipped with a fuse? Anyway, I don't know if the rear wiper is the cause (it was not in use for the last 2 months) and the problem is that the owner's manual supplied with the car is not exact and probably refers to older models (my car is a 2000 production, has the older shape but is supplied with the AL4 auto transmission...) What do you mean by "the light in the dash"? Do you mean the one in the trunk? Well, I've noticed after the fire that it is on constantly with no apply to the doors situation, but I do not know if it was on all the time before. The car is in the garage now and I will inform you later what is going on.
Thanks again – Michael.
I think jeremy could be right with the lack of fuse in some circuits, and brakes are high wattage bulbs, and i would assume you may have 3 lights, a centre one having a many bulbs... hence a lot of current compared to say a tail light
what i mean by a light in the dash is... when you put the rear window demister on, then an orange light will come on at the dashboard indicating it is on, so if this bulb behind the dash doesn't work, how do you know the rear window demister is off? how do you know the timer is stuck, so that it's always on?
of course being a rear window demister it will be a fused circuit, but this does not mean a previous owner put the right fuse in, lets assume it's a 15amp fuse, maybe someone put a 20amo fuse in it, this would obviously let more current down the circuit and may melt wires causing a fire.
Disclaimer: I'm not an auto electrician though! I'm just a car enthusiast.
what i mean by a light in the dash is... when you put the rear window demister on, then an orange light will come on at the dashboard indicating it is on, so if this bulb behind the dash doesn't work, how do you know the rear window demister is off? how do you know the timer is stuck, so that it's always on?
of course being a rear window demister it will be a fused circuit, but this does not mean a previous owner put the right fuse in, lets assume it's a 15amp fuse, maybe someone put a 20amo fuse in it, this would obviously let more current down the circuit and may melt wires causing a fire.
Disclaimer: I'm not an auto electrician though! I'm just a car enthusiast.
reverting to the topic :
most fuses wil protect several consumers in one circuit. Thats why you sometimes find a 25Amp fuse circuit with a connected lamp only consuming some 1.5Amps.
If you apply Ohm's law you can then get a permissible 12V x 25Amps = 300watts power consumption on that fused circuit. In fact you can get even higher wattage consumption as the 12V supply mostly is approx 13.5V when engine and alternator is running and charging, plus the fact that the fuse will only burn out if it is well beyond its rating, say +50%.
Then the calculation should be changed to : 13.5V x 37.5Amps = 506Watts.
500watts or thereabouts is more than adequate to white heat a well heavy gauge wire and quickly set off a fire in nearby cloth materials.
Even 200watts or less can do this, depending on the wire gauge.
Its all about production costs savings for the manufacturer - and very little about protecting against that single incident in 5 years pr statistics.
most fuses wil protect several consumers in one circuit. Thats why you sometimes find a 25Amp fuse circuit with a connected lamp only consuming some 1.5Amps.
If you apply Ohm's law you can then get a permissible 12V x 25Amps = 300watts power consumption on that fused circuit. In fact you can get even higher wattage consumption as the 12V supply mostly is approx 13.5V when engine and alternator is running and charging, plus the fact that the fuse will only burn out if it is well beyond its rating, say +50%.
Then the calculation should be changed to : 13.5V x 37.5Amps = 506Watts.
500watts or thereabouts is more than adequate to white heat a well heavy gauge wire and quickly set off a fire in nearby cloth materials.
Even 200watts or less can do this, depending on the wire gauge.
Its all about production costs savings for the manufacturer - and very little about protecting against that single incident in 5 years pr statistics.
Anders (DK) - '90 BX16Image
Well, the car is ok now. The electrician replaced the burnt wire all the way from the fuse box to the rear. He found out that the wire (that was in charge of the back windows screen) suffered from the back door of the trunk, which with its actuation stripped it from the insulation on one place where it made a shortcut to the body or frame of the car. I wonder how this could be, as the body is painted all over and inside? He worked 7 hours on my car, and charged me 1000 NIS, which are about 122 UK pounds (150 NIS for one garage hour). The work is a clean one and every thing was put back correctly.
1. What do you think about his explanation regarding the cause of the fire?
2. What do you think about the price?
Regards – Michael.
1. What do you think about his explanation regarding the cause of the fire?
2. What do you think about the price?
Regards – Michael.
I'd have thought the price was good - here I'd expect a minimum of £40 per hour!
Car electrics are very time consuming as everything is hidden behind trim which has to be removed, and even when that is done the bits you want are often very difficult to get at!
I'm a bit surprised that it should be the heated screen as its operated by a switch and a timer and as far as I know the ones with timers (our ZX has one so presumably the Xsara has one as well) cancel when the ignition is turned off and need to be set every time they are used.
With a simple switch it would be possible to leave the thing on for ever - with a timer it'll cut out after 10 minutes - and needs to be set whenever its used.
Strange - you're the second case of an electrical fault on a Xsara in the tailgate wiring that has come up on here in a week!
Yes the body is painted - but flexing will eventually scrape off the paint. It sounds as though there may be a problem here - like wrong length wiring causing stress, poor installation meaning that the wiring didn't run quite as it should, poor previous repair or something which has caused the short probably a long time afterwards.
Car electrics are very time consuming as everything is hidden behind trim which has to be removed, and even when that is done the bits you want are often very difficult to get at!
I'm a bit surprised that it should be the heated screen as its operated by a switch and a timer and as far as I know the ones with timers (our ZX has one so presumably the Xsara has one as well) cancel when the ignition is turned off and need to be set every time they are used.
With a simple switch it would be possible to leave the thing on for ever - with a timer it'll cut out after 10 minutes - and needs to be set whenever its used.
Strange - you're the second case of an electrical fault on a Xsara in the tailgate wiring that has come up on here in a week!
Yes the body is painted - but flexing will eventually scrape off the paint. It sounds as though there may be a problem here - like wrong length wiring causing stress, poor installation meaning that the wiring didn't run quite as it should, poor previous repair or something which has caused the short probably a long time afterwards.
jeremy
I forgot to mention that the radio is dead now; I mean it receives current but the stations that where saved in its memory are gone and only 3 lines are visible now. What is the method of bringing it back to life again? I can remember a switch procedure or something like that. Is it possible to restore its memory? It is an original device – not one fitted by the importer.
Cheers! Michael.
Cheers! Michael.
Hi Susoni
If the radio display is now showing three lines, then it has while the electrician has been working on your car, had it's power supply turned off, I.E. the battery has been disconnected. So the display you now see on the radio probably, means it needs the security code to be put in.
Also please let us know where you are based I.E. which country are you in ?
If the radio display is now showing three lines, then it has while the electrician has been working on your car, had it's power supply turned off, I.E. the battery has been disconnected. So the display you now see on the radio probably, means it needs the security code to be put in.
Also please let us know where you are based I.E. which country are you in ?
