Melted battery lead (Urgent)

scoles · Post by **scoles** » 27 Dec 2009, 09:50

Hi people, done 900 miles trouble free driving since i got the xantia running again.

but went out yesterday and started the car and turned on the rear window demister and the front window blowers to full.

the car was in the drive so i went in and gave it a few minutes to warm up and clear.

When i came out and opened the door all i could smell was electrical burning and i noticed smoke coming from under the bonnet.

Anyway lifted the hood and the positive lead coming from the battery is completely melted and the cores are white.

The heat coming from the cable was pretty high.

I just cant think of what is overloading this cable that much that it melted so badly.... it only starts to get seriously hot when things like the blower motor is on and the rear window demister is on.... i know these both draw a fair bit of current but i wouldnt have thought it to be enough to do that damage.

So looking for some ideas as to the cause?

Cheers
Stuart

DickieG · Post by **DickieG** » 27 Dec 2009, 09:57

I'd take a close look at the ignition switch for a short.

Post by **RichardW** » 27 Dec 2009, 10:01

Is it an estate? If so , check the state of the wires running to the boot though the rubber conduit - they can break, and this might be giving a short to earth if you are unlucky...

scoles · Post by **scoles** » 27 Dec 2009, 10:06

The car is a xantia saloon, the ignition switch was mentioned how would i go about checking that for a short?

Only thing i found strange i fitted a cd player that morning, but no wire cutting was involved simply plug and play and it works.

Need the car for work on tuesday badly.

Cheers
stuart

Post by **CitroJim** » 27 Dec 2009, 10:40

The feed to the heated rear window and the blower are both individually fused so any short beyond the ignition switch would have blown the respective fuses.

For such a heavy short you have to look between the battery, the engine fuse box (the supply is fed via one of the giant fuses in the engine fuse box) and the ignition switch.

I agree that the switch may well be the guilty party. Slip off the cowling under the steering wheel and see if the heavy wires going to the switch look at all distressed. Check too for chafing.

I can't recall if the car in question is a MK1 or a MK2. let me know and I'll supply applicable wiring diagrams.

HDI · Post by **HDI** » 27 Dec 2009, 11:03

Shorts or overloads on any circuits should pop a fuse. My vote goes to a high resistance battery cable.

Post by **RichardW** » 27 Dec 2009, 11:12

Thinking about it, +ve lead goed direct to the starter doesn't it? So, either fault with the starter running on, or the cable was damaged and earthed itself somewhere?

It's an HDi Jim, so it must be a MK2

scoles · Post by **scoles** » 27 Dec 2009, 11:25

a few pointers in the above info there.

Would i not hear the starter running on? i conducted a wee test yesterday and with the car running the cable stayed cool but as soon as anything was demanded through it ie blower or demister it started heating it.

It got hot enough to start the colder running from the battery terminal.

at my wits end here, the weather just is not good enough to check anything

Post by **CitroJim** » 27 Dec 2009, 12:23

Stuart,

Can you please identify exactly which cable is getting very hot as there are at least two running from the positive pole of the battery.

The big heavy one goes direct to the starter/alternator and there will be a second, slightly smaller cable that runs up to the engine bay fuse box and terminates on a busbar supplying the three or four giant fuses in there (the ones rated between 40 and 80A.

Am I right in thinking it is the smaller of the two cables that is overheating?

Where are you located Stuart? Weather is not that bad down this way...

scoles · Post by **scoles** » 27 Dec 2009, 13:16

both cables have melted, wether this is because both have overheated or because they are both side by side and one has melted the other.

I am based in fife and its not stopped raining all day.

I am nipping out just now to have check at the fuse board beside the battery and the cables.

Cheers
Stuart

Post by **Peter.N.** » 27 Dec 2009, 13:53

Check that the cable from the battery is in good condition and that all the strands of wire are making contact, if its only connected by a few it will get hot.

Peter

scoles · Post by **scoles** » 27 Dec 2009, 15:05

Small update,

Been out and removed all the sheilding from the cabling and there are four wires going to the +Ve on the battery

Four cables were mostly fused together heading down the cable about 6 inches. and a were bare in some parts. (unsure if this could have caused a short as they were only touching each other)

3 x thinner cables that run into that fuse box
1 x starter cable.

All are fried as you will see with the pictures.

I have temporarily cleaned them up and re wound the outer sheath.

plumbed the battery back in and temp clamped the cables back on.

started it no problem and switched everything electrical off.

introduced the rear demister and blower and two of the smaller cables started to get warm but deffo not hot.

I done a continuity test on these cables to the big fuses and i am sure one goes to fuse F and the other fuse B..... which are both 40 AMP fuses that are not popped.

heres some pictures.

and the battery clamp had melted off

Unfortunately my meter only goes to 10 amps

Cheers
stuart

Post by **Peter.N.** » 27 Dec 2009, 15:15

To do that much damage I would think that you would need starter motor type current, several hundred amps, the only other thing that takes a fairly substantial current are the glow plugs, about 80 amps on a non HDi engine. When you have repaired it check the battery voltage with it running and without and see if it drops much below 12v.

scoles · Post by **scoles** » 27 Dec 2009, 15:30

i checked the battery voltage with it running and it was in the region of 20 volts.

and just under 13 volts not running.

the started cable is cool though

Stuart

Post by **CitroJim** » 27 Dec 2009, 15:52

scoles wrote:i checked the battery voltage with it running and it was in the region of 20 volts.

Ahh, bingo! You have a faulty alternator! It should produce absolutey no more than 14.4V when on charge. I'd say the alternator is running uncontrolled and putting a massive current through the battery and thus melting the cables. Essentially it is massively overcharging.

Run too long like this and the battery will explode. Prove this by disconnecting the thick cable to the alternator and insulating it well.