Electrical Problems

[theo thomas]

I'm being plagued by an erratic but catastrophic electrical fault that causes all power to be lost (the main 40A fusible link blowing - now relaced by 2x20A fuses in parallel)that I can't identify. Anyone any ideas for techniques for identifying the cause / remedy ? The loom was supplied by Marlin originally, and I have no wiring diagram!

[h_m_cumming]

Re: Electrical Problems

Theo, if it's possible, try disconnecting each wire that is connected on the outgoing side of the fuse in turn and then go round all the wireing that you can get at and move it around to see if you can replicate the fault. It certainly sounds like a rubbed through wire or a loose wire shorting to earth [or another earth wire] causing the fault.To blow a 40A fuse is a major short.

[theo thomas]

Re: Electrical Problems

Thanks for your reply Hugh. I've removed all the fuses (as I have no wiring diagram I dont't know which one does what anyway) and I've wired in a temporary 12v 1A supply instead of the battery. I've also put a 5w bulb across the where the 2x20 fuses should go. On ign switch click 1 the bulb pulses on/off which I think must be the ECU. On click 2 the bulb lights fully. That's telling me I have a dead short I think! Without stripping down each and every component that the switch is feeding I'm struggling to continue. Any more thoughts?

Theo

[h_m_cumming]

Re: Electrical Problems

Theo, on the output side of the 2x20, how many wires are there?
If you want to contact me by e-mail, it's huron[at]roxanne37.fsnet.co.uk
I think first thing is to try and tie it down to one of the wires on the output side.

[pdm_engineer]

Re: Electrical Problems

Theo
Sounds like a nasty problem you have. however if it`s a permanant fault now, it should be a lot easier to find.
Firstly I have been infomed by someone, and I can`t remember who, that the Marlin Loom is supplied by Premier Wiring Systems tel 01483 715725. A call to them may yield a wiring Diagram if indeed they do supply it.
Secondly from your above test I would say that does not neccessarily mean there is a dead short, it just means there is a lowish resistance to ground, probably in your case via the ignition module.
I did`nt use this loom myself so is alien to me as well, but one question for you is: how is the fuel injector supply wired in. On the sierra loom it has a relay directly connected to the fuse link wire, and the output is unfused.
The other unfused parts wired to this fuse link are probably:
a) The thick red wire to the ignition switch and the black/yellow (or other thick wire) from the ignition switch to the fuse box.
b) The black wire to the ignition module and the module itself.
c) The black wire to the injectors in the Ford engine loom.
d) The wires to the input of any relays are likely to be wired to this Fuse link as well.
e) worth a mension also is the Engine coolng fan as this could be wired here as well.
If your loom follows the standard Ford colour scheam all battery wires should be Red and all other live feeds should be black or black with one other tracer colour.
I`m affraid that the only way to locate faults of this nature is to remove bits until you find the cause , but in my experiece is usualy a damaged wire somewhere. On the marlin have a good lood around the steering collumn and where your loom passes close to the wiper operatiog rods.
Your wellcome to contact me by phone if tou still have my number or Email to Peter(at)morris504.fsworld.co.uk
Refuse to leave Phone details here though.
All the best
Peter

[amalgamated users from prior forum]

Re: Electrical Problems

Message originally posted by: Keith Howell
I have the complete set of Ford Sierra wiring diags from Ford. Patently I can't photocopy the lot but if there are any particular bits you think you need let me know and I will try to scan the pages and email them. Alternatively, I live in Prestwood in the Chilterns, probably no more than an hours drive, if you want to come over and have a peruse of them. (With the best will in the world, I would be reluctant to let them go)

[amalgamated users from prior forum]

Re: Electrical Problems

Message originally posted by: Sue Roedel (Editor, MOC)
Theo,

What's wrong with your \\\ keyboard?!

I've editted your posting for you as it was making my eyes go funn\\\y.

[amalgamated users from prior forum]

Re: Electrical Problems

Message originally posted by: /////
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[theo thomas]

Re: Electrical Problems

Many Thanks to all of you who replied re. my electrical shorting dilemma. I've now solved the problem by dismantling/eliminating things one by one, whilst applying the 'wiggle test' to the loom. It has taken hours! Turns out it was the ignition-fed line out to the fusebox that had rubbed on the steering column upper flange (just behind the switches) - well out of sight and mind!. All I have to do now is refit everything I've taken off. Should be back on the road soon, hope to see you at the AGM at Stoneleigh.
Thanks again.