Confused! Leisure battery fuse blowing

[tandemsandy]

...and that's even before the engine is turned on!
Thanks to the info on here I have found and checked the split charge relay. It appears to be triggered by the ignition, not the alternator wire, as it energises as soon as the key is in the 'run' position. Problem is that as soon as the relay pulls in, and before I try to start the engine, the 30A fuse blows at the LB.
Its a 1984 Leisuredrive, though I have to say the wiring I've found seems less that professional in places! There is a zig cp400 distribution board.
There's a 12v feed from the VB to the relay, then a return that splits, going to the LB and I guess to the zig.

The fuse is blowing even though nothing is switched on, so I'm thinking the 12v from the relay is earthing somewhere causing the fuse to blow. Am I barking up the right tree? Want to get the stereo wiring up to the LB, but not much point while I can't charge the LB!!

All words of wisdom appreciated!
Yours frustratedly,

Rob

[billybigspud]

for that to blow you must have a dead short +ve -ve. you need to check the circuit like you have said. get a multi meter and set it to continuity and check go through checking between body and +ve. take it apart as you go so you can eliminate each part. either that of just re wire it. wont take you long and it the existing is that crap you will have piece of mind.

[BOXY]

Is the leisure battery completely flat? If it is it might be pulling enough amps from the starter battery to blow the fuse? Try disconnecting the leisure battery and see if the fuse blows. If it does you'll know the short is downstream of the battery, if it doesn't try charging the battery and see if it holds a charge before refitting it.

[Oldiebut goodie]

either that of just re wire it.wont take you long and it the existing is that crap you will have piece of mind.

What's this bit in English?

[1664]

either that of just re wire it.wont take you long and if the existing is that crap you will have piece of mind.

What's this bit in English?

just a typo

[Oldiebut goodie]

I think that we need something to describe the mangling of the English language - how about to ' T-bone' (named after that well known mangler of English in his posts on the forum).

[tandemsandy]

Thanks, glad to know I was on the right lines!
Have replaced the wires to & from the relay, fuse still blew. The relay has two sets of switching poles, like 2 relays back to back. One set of poles pull in the charging circuit, the other connect to the fridge, if I've understood things correctly its so the fridge runs off the VB (ie alternator) while driving, then drops out again when the engine is off. If I pull the fridge leads from the relay, VOLA! No blown fuses and both batteries charging according to the multimeter.

So, conclusion is that the fridge is earthing somehow when in 12V van battery mode, thus drawing loadsa amps and shorting the LB. Does that make some sense to somebody?????!!!!!

Rob

[Oldiebut goodie]

Seems to be a good starting point. Maybe someone has trapped a cable when replacing the fridge?
Just re-reading your last post you say about removing the wires (plural) from the relay that go to the fridge - there should be only one positive from the relay to the fridge usually.

[tandemsandy]

Ah, think my turn for a typo!!! 'leads' should've been 'lead' !!!

Stereo all wired in and working now, happy days

[billybigspud]

either that of just re wire it.wont take you long and if the existing is that crap you will have piece of mind.

What's this bit in English?

just a typo

you would think i typed properly with the amount of typo's i make, not with two fingers stabbing away at the keyboard.

[California Dreamin]

This one is pretty easy to explain....
BECAUSE someone wired the relay incorrectly to power with the ignition, the STARTER motor is using the LEISURE battery AS WELL as the starter battery to start!
And as the starter on a petrol engine draws around 160amps that puny little 30 amp fuse is going POP!
You just need to rewire the relay so it gets it's 'switch feed' from the alternators charge wiring (charge light circuit) so the relay ISN'T connecting the two batteries together until AFTER the alternator starts charging (engine running)

Simplez.....
Martin

[Oldiebut goodie]

^^^^^^Makes sense.
I was automatically thinking that it was a voltage sensing relay due to the way it was wired!

[BOXY]

...and that's even before the engine is turned on!

I was reading that as the fuse was blowing as soon as the key was turned to "on", one click before the starter was cranking? I'm not disputing that the relay needs re-wiring tho'

[tandemsandy]

Yep, fuses were blowing in the 'run' position, not when cranking (they'd already blown before the key got that far!!) Does seem like a stray live wire was earthing the fridge feed, all been fine since they were disconnected.

Have added 'rewire relay trigger' to the 'to do' list

Thanks for all the help guys.

Rob