electrical burn out

[feardana]

Hi - when we were on a site recently and hooked up to the mains i got a strong burning plastic smell and discovered that the wiring running off the car battery to the leisure battery had completely melted - it was so close to the fuel line that that also melted. I disconnected the wiring from the leisure battery and traced the wiring which was originally coming off the car battery and i can fix this myself but since i'm not exactly sure what happened in the first place i need to diagnose it properly - i have an idea what caused it from researching online but since it's electrical and not my area i wanted to get good advice on if first, we don't have the bus that long, (it's an 1985). I should mention that when we were on the previous site and hooked up to AC we couldn't get enough power to run the fridge etc and almost immediately after arriving on the new site and hooking up the wires melted. Any help would be much appreciated, many thanks

[1664]

Not really enough information. The incident may not be anything to do with the mains hook up at all.

Is your van a recognised conversion like Autohomes, Holdsworth, Leisuredrive etc?

Do you have a mains powered battery charger?

Since it nearly caught fire I assume the split charge system was not fused in any way? What does (did) the split charge system consist of exactly? Might be a straight forward short to the bodywork.

[feardana]

Hi, yes leisuredrive -

don't know if the battery is being charged by the mains, what should i look for to check?

not sure about a lack of fuses, i just assumed it had the necessaries but i'll check if someone can point me in the right direction

i don't know what kind of split charge system exists, there's a mains fuse, switch and box beside the leisure battery which i was assuming was also the split charge relay? don't know if any other hardware exists between this point and the car battery

the wires melted a couple of feet in from the car battery but seem to be fine after that so would that suggest a short on the body?

[1664]

Right, the Leisuredrives I've seen have not had battery chargers fitted and the leisure battery has been charged by a simple (fused!!) split charge relay arrangement. The leisure battery supplies a simple CP400 unit which in turn supplies the camper circuits via 10A fuses. The Zig can switch between which battery supplies these circuits, starter of leisure. This does not however rule out a 'DIY' mains charger addition by a previous owner.
The Leisuedrive mains installation only consists of an RCD main switch with two circuit breakers; the smaller circuit breaker (6A) supplies the single socket the fridge is plugged into and the larger breaker (10A) a twin socket for general use. That should be it (in my experience)
You are going to have to rewire your split charge system whatever happens and there is plenty of information in the club 'Wiki' under "Camper Electrics" on this subject.
12v won't kill you by electrocution under normal circumstance but it can't half set fire to stuff if it gets across those terminals and remember the bodywork is one giant negative terminal.

[California Dreamin]

I'm not sure why wiring like this is anywhere close to fuel lines

What is the state of the leisure battery? just wondering it there isn't a dead short in the battery that has caused this?
Also
Do you know how flat the leisure battery is? there can be large currents flowing on initial start with a flat leisure...

Martin

[feardana]

ok, that's very helpful - it says CP3G on the zig plate and all 3 10A fuses are fine - just to say as well that the mains supply worked fine after the wires burned out - do you think it's likely that the wires shorted on the body?

why is it a given that the split charge system needs to be rewired?

As for a diy mains charger i don't think so but i'll try to find out for sure

regards

[feardana]

i agree martin, the wires coming off the car battery were bundled with the fuel line - thankfully diesel is hard to combust but still

as for the leisure battery i'm not sure what your asking - at the time it happened the leisure battery should have been fully charged as we had driven for a few hours - i disconnected the battery then and haven't reconnected it since but it may well be dead by now as it hasn't been connected to the engine for a while

how would a short in the leisure battery cause the wires coming off the car battery to overheat?

also, why would there be a current running in the wires coming off the car battery if we were hooked up to the mains and there wasn't anything running except the fridge off a socket?

in fact, is it possible for someone to explain these different circuits or maybe correct me if i'm wrong here but the way i understood it was that the leisure battery is charged by the car battery while the van is running - this passes thru a relay and into the leisure battery which in turn can be used to power the lights/pump etc. Anything else run off the sockets can only be powered by an AC power supply from a mains and there may or may not be a leisure battery charger which is fed from the mains as mentioned by 1664. The switch on the zig plate, car/van allows you to run the DC circuit off the car battery if the leisure battery is flat - is this more or less correct?

[MidLifeCrisis]

in fact, is it possible for someone to explain these different circuits or maybe correct me if i'm wrong here but the way i understood it was that the leisure battery is charged by the car battery while the van is running - this passes thru a relay and into the leisure battery which in turn can be used to power the lights/pump etc. Anything else run off the sockets can only be powered by an AC power supply from a mains and there may or may not be a leisure battery charger which is fed from the mains as mentioned by 1664. The switch on the zig plate, car/van allows you to run the DC circuit off the car battery if the leisure battery is flat - is this more or less correct?

That is pretty much correct - but is only has it is supposed to work, not necessarily how it is working.

The main concern here has to be that the wire from your starter battery going to the split charge relay was not fused near the starter battery (as it should be) which allowed the wire to melt (when whatever went wrong went wrong)!

Take a look at the Wiki for full details of how a split charge system should look;
https://club8090.co.uk/wiki/Ca ... it_charger

It may have been a simple case that the wire was old and frayed and just happened to short to the chassis while you were on hook up and stationary .....
..... but it could be that there is something far more sinister going on with your mains hook up system that you need to investigate .....

You need to start following/documenting wires in the van systematically until you are confident that you know what every wire does, where it goes and if it is correct ..... (including the mains wiring) .... or if you are not confident in your ability to do this then get someone who is to give it a once over just for your own peace of mind ... sounds like this could have all gone a lot worse than it did .... no one likes to hear "..wiring running off the car battery to the leisure battery had completely melted - it was so close to the fuel line that that also melted.." !!!!

[1664]

why is it a given that the split charge system needs to be rewired?

because of this:

got a strong burning plastic smell and discovered that the wiring running off the car battery to the leisure battery had completely melted

you're not planning on re-using it surely?

[feardana]

To 1664, no i wouldn't reuse it if the wiring was completely compromised but if it was frayed in one area and then shorted on the body and the rest was fine then i was wondering why it was a given that the whole thing needed to be rewired, i had intended to get a professional to take a look at it anyway but i wanted to talk to people who have specific experience with T25 electrics first - i thought from what you said about rewiring that maybe other parts of the system may have been compromised by the burn out and i just wanted to clarify that.

To midlifecrisis, many thanks for that - i don't know why this part of the circuit wasn't fused, i'll follow the link you gave me and i'll get the electrics fully checked out - many thanks

if anyone else has any advice i'd be grateful

regards

[feardana]

ok, i had a look at the wiring diagram on wiki and checked out the van and this is what i'm seeing -

running from the alternator there's 2 red/white wires and these connect to the car battery (+) terminal which i'm assuming are what charge this battery - there's one red wire running off the battery towards a fuse box in the engine which i'm assuming goes towards the ignition?

the other 2 wires coming off the alternator are blue and brown/black in colour - these run to a small fuse compartment and coming out the other side of the compartment are 2 wires which look green and a darker green colour and these wires as well as the red wire coming off the car battery run to the fuse box i mentioned.

The wires that melted were running off the positive and negative terminals of the car battery - these were blue and brown as far as i can tell though after the melting i'm not 100% sure - i can see them going up into the van and i've tried to find them inside but at the moment i can't - i'm prob going to have to rip stuff up to get at them

I always assumed that the wires that melted were there to charge the leisure battery but looking at the wiki diagram i'm not so sure now - here's a wild stab in the dark but the only wires inside the van which match the ones that melted are the ones powering the pump for the sink - is it at all possible that these may be connected directly to the car battery? (excuse my stupidity if this clearly demonstrates it) - to operate the pump it has to be switched on at the zig panel and i always assumed that it was running off the leisure battery but the more i think about it now i'm not so sure - the leisure battery is dead so i can't check that out at the moment

i am going to contact a spark that i know - it's not easy here to get people who have expertise in vws - they're in short supply, generally a long drive away, have big waiting lists and the last guy we dropped the van into kept it several months after he said it'd be ready and charged thru the nose for the work so the more i can do myself the better - i appreciate that people on the forum are prob reluctant to give advise on something that's potentially very dangerous, i get that but any ideas or prior experience related to this would be appreciated and i will get the whole thing fully checked out once i'd done here, i just want to try to get some knowledge before i bring it to someone

many thanks

[MidLifeCrisis]

the other 2 wires coming off the alternator are blue and brown/black in colour - these run to a small fuse compartment and coming out the other side of the compartment are 2 wires which look green and a darker green colour and these wires as well as the red wire coming off the car battery run to the fuse box i mentioned.

There's usually only one wire (other than the two red/whites) coming off the alternator - this wire goes to the battery indicator light on the dash. However this is also the wire that is spliced into to trigger the split charge relay; so its possible that the brown/black wire is doing that?? Can you trace it to the split charge system.

The wires that melted were running off the positive and negative terminals of the car battery - these were blue and brown as far as i can tell though after the melting i'm not 100% sure - i can see them going up into the van and i've tried to find them inside but at the moment i can't - i'm prob going to have to rip stuff up to get at them

It's strange that both a positive and negative connected wire have melted - does it look like they both melted independantly or do you think one melted and melted the other.
It's not normal for there to be a negative wire returning to the battery terminal - usually items are grounded to the vehicle itself - so this might suggest that this is a 'pervious owner added item' ...... weird !?!?!

is it at all possible that these may be connected directly to the car battery? (excuse my stupidity if this clearly demonstrates it)

It's not impossible but would not be normal operation - and as you say that the Zig has to be switched to allow the pump to work then that suggests that the pump is connected to the leisure ... assuming that the Zig is connected to the leisure and not just to the starter battery ....???

Final note - if those burnt wires are going to the pump ... does that leave any remaining wires from the starter battery positive that 'could' go to the split charge system??
Final/Final - add your vehicle and engine type to your signature so people can see what engine type etc you have when answering questions!!

[CJH]

The wires that melted were running off the positive and negative terminals of the car battery - these were blue and brown as far as i can tell though after the melting i'm not 100% sure - i can see them going up into the van and i've tried to find them inside but at the moment i can't - i'm prob going to have to rip stuff up to get at them

Can you see which direction these wires go in? Is it possible they go forwards to the dash? As MidLifeCrisis suggests a) it's likely something that a previous owner has added (because of the -ve connection) and b) it's odd for both wires to melt. If they've both melted independently it suggests that rather than there being a nicked/damaged wire causing a short, maybe there was just too much current going through the circuit for those wires to take. I'll take a wild guess and suggest that these wires might feed a cigarette lighter socket that's been added by a previous owner. Did you have something running off a cigarette lighter at the time you smelled burning?

[feardana]

The wires coming off the car battery going to the relay were bundled together so it's quite possible that only one melted

i don't think anything else was running off the car battery

so those blue and black wires running off the car battery ARE part of the leisure battery charging system then? but your saying that usually there's only one wire running off the +ve terminal and the other is grounded to the van so it wouldn't be connected on the way back to the -ve terminal on the car battery? why might someone do this then?

also, in the wiring diagram in the wiki, what is the green wire running directly from the alternator to 86 on the relay? and what is the purple wire running from the battery to 30? - just need clarification on that

i can try to trace it to the split charge system, where abouts is it normally located?

i don't think the zig is only connected to the leisure battery because when i disconnected the battery the dc power went

so for the wires coming off the car battery going to the relay, where are the fuses normally located in relation to the battery? does it not seem strange that no fuses exist?

apart from the wires getting frayed and shorting on the chassis, what else might cause something like this?

also, if someone did a diy and put something in to charge the leisure off the mains, where might it be positioned?

sorry, the more i'm learning the more the questions are coming

[feardana]

to CJH, there may have been something running off the cigarette lighter at the time but i can't say for sure, we were using a sat nav but it's all a bit hazy at this stage

as i said in the last post the 2 wires were bundled together in a common flex so it may well have only been a problem with one of them

i can see the wires going up into the van, (heading in the direction of the zig which is one of the reasons why i thought they might be connected to the switch for the water pump), but i haven't found them inside yet so i don't know where they're going once they enter the van

if these wires were powering the lighter then how does that tie in with the split charge relay/leisure battery charging mechanism?

many thanks