Totally dead, totally stumped HELP please!

[LeeME3]

OK so after a whole day of chasing around I'm a little wiser but not much...

Decided the time had come to sort out the mess of the leisure wiring and quickly discovered the stereo was connected to the starter battery (for memory) and leisure battery (for operating power). Decided to switch it all over to leisure but first of course disconnect both batteries... (later fuse box blade style)

So, intending to slide the driver's seat forward (RHD so starter battery behind driver) I slid backwards (yup, recently sorted out my rails so they run nice and smooth) and ended up with the seat shorting out the battery (there are normally covers in place but of course I'd removed them in prep for battery disconnect - yes, i'm a VERY silly boy). She was shorted for a good few seconds with a lot of smoke off the battery terminals and sufficient heat to crack the top of the battery case.

Immediately checked all the fuses - nothing blown. Put a new battery in and totally dead. Not so much as flicker on the dash. So, went through the following:
Removed ALL stereo wiring and any other after market stuff I could trace and removed leisure batt so that is out of the equation
Checked power getting to fusebox at terminal 30, it is, and back out to the back of the ignition switch
Removed fusebox and cleaned up all connections
Split the fuesbox - no burn damage inside (it is a work of art in there mind...kind of a 3D circuit board, looks almost Swiss)
Tidied a few less than perfect earth connections on the 2 earth crowns to the left of the fusebox
Put it all back together - still dead
Even tried a jump from the power supply to the ignition switch to the light supply to the switch (black and yellow) but couldn't even get the headlights to wake up
Measured voltage across battery - about 8v, hmmmm...
Disconnected all connectors in the back of the fusebox in turn and same for relays
When block B (instrument cluster connection coloured red) and / or relay 18 are in position the batt terminal voltage is about 8v, remove them both and she goes back to 12+v
Checked and re-checked everything without going so far as undoing the main loom (um, no thanks) but can't see any physical damage or find any scorching
Confirmed power getting to ignition switch - yup, 12+v when the relay and / or connector B removed, 8v when either / both fitted
Removed and confirmed operation of relay 18 on a known good battery - all good
Put it all back together and came inside to plea for help....

Any ideas? For me something between connector B and the ignition switch / instrument cluster is taking the voltage down (well, draining current to be entirely accurate I suppose) but how is that connected to the short without signs of physical damage (not that I can see the entire loom of course)?

Of course the van is needed in a couple weeks for a half term trip away...if I can't solve it tonight she'll be off to Camper shack providing they can fit her in

I normally get there in the end with electrics by being careful and methodical...this one has got me. Thanks in advance.

[tonytech]

How are you measuring the voltage across the battery? 8V is knackered. Are you connecting to the battery terminals or the cable clamps.Are the terminals nice and clean?

Have you checked and cleaned the battery earth cable? Check where it connects to the chassis.

If you slid the seat back onto the battery, then the damage must be in that area, either the seat has bridged the +ve and -ve terminals of the battery or the seat has touched the +ve terminal and current has flowed through the seat to the vans chassis and to the -ve through the battery earth cable.

T

[LeeME3]

Thanks Tony. Having spoken to the ever helpful Andy at Campershack today we're coming to the feeling it is most likely that I actually shorted the live to the earthed vehicle rather than across the terminals. The battery reads 12v+ at the terminals until I connect multi-connector B into the back of the fusebox then it goes to 8v suggesting something in that sub loom is shorting out. The positive terminal is very badly damaged but the negative is fine (on the battery I shorted - clearly I'm using a known good and undamaged one for the fault finding!). I Think this also suggests a positive to vehicle earth short.

Next time I'm at the vehicle (thurs) I'm going to try creating a fresh earth strap with a decent quality jump start cable from battery to chassis just to make doubly sure I do have decent earth. I can read 12v+ if I connect a multimeter between battery positive and the earth crowns but of course that's under no (minimal) load.

I've also ordered a new ignition switch from Brikwerks, mainly to discount that as a possibility as they are famously fragile and a good belt of current won't have helped it!

Gut feeling is something is fried in sub loom B but extracting that from the main loom doesn't strike me as a pleasant, quick or easy task....

Got a date for her to go into Campershack so I'll try a few things but no doubt have to fall back on their considerable expertise.

Still REALLY annoyed with myself....and I'm going to have to go to van jamboree in a non VeeDub and sleep in a tent! Aaaaaaarrrrggghhhhh

[chapperss]

Sounds like its probably the earth cable/connection to the body. the high current passing though this during the fault would probably have knackered it. If you shorted the positive terminal to earth with your seat, then I cant see how any other part of the electrical system would be effected( I'm and electrical maintenance engineer) as the current would have gone directly to the body, not thought anything else( it always takes the easiest route). I bet if you measured fron the negative terminal to the body somewhere(like your earth crowns) with a voltmeter you'll find the missing volts ie will read about 4 volts if I'm right.

[LeeME3]

Chaperss I"m liking the logic there - I'll try it tomorrow when I'm back at the van, cheers

[nevill3]

I recently had a mishap with my leisure battery, a previous owner had "wired" the radio up without a fuse and connected the wires by twisting them together. They came apart and shorted out on the dash. When I checked everything afterwards I found a very thin black wire had been used as an earth for an extra cigarette lighter. This wire had melted even though it isn't directly connected to the radio circuit. I also found a fuse I never knew I had, it was tucked in the trim panel at the end of my rear wardrobe, this is the fused link for my Zig unit, I was getting very strange results until I found it.

Maybe you have a blown fuse somewhere that you don't know about?

[ghost123uk]

The battery reads 12v+ at the terminals until I connect multi-connector B into the back of the fusebox then it goes to 8v suggesting something in that sub loom is shorting out.

To me this is 99% that "new" battery is faulty.

Any short that dropped the voltage on a new battery to 8V would be drawing so much current summat would be smoking. Try another known good battery, even if you have to just borrow one of a mates car (though check the position of the +ve and -ve as on some vehicles they are at opposite ends of the battery).

[LeeME3]

I'm pleased to report that at 1425 this afternoon 'Snowdrop' was successfully revived and taken off of life support. She is now breathing on her own and, whilst not yet able to move under her own power, is expected to make a full recovery in time for Lincoln Van Jamboree.

Many thanks to all your inputs and especially big thanks to Andy at Campershack for his patience and logic on the phone.

In many ways pretty much everyone was right...we had a combination of bad earths, dodgy batteries, iffy ignition switch, bad connections in to the fuse box and some 'interesting' repairs to the main loom.

Ultimately working round everything in turn constantly checking, cleaning, tightening and when in any doubt renewing has brought her back from the dead. There's a couple bits still to tidy (hence her current immobility - not going to risk a break down) not least of all re-wrapping the loom I've had to break into to find and sort those dodgy repairs (I say 'I', actually the old man did it - cheers Dave!).

Thanks all and see you at VJ those that are going!