Annoying mystery electrical fault

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Annoying mystery electrical fault

Postby JohnandJo2005 » Wed Sep 06, 2017 8:48 pm

The "re-commissioning" of Bertha has ground to a stop because of an electrical fault that's got me stumped. Bertha is a 1956 series 2 split screen four door saloon. I've installed a new loom and have had the engine running on the original pull starter with the bulk head mounted solenoid. Now all of a sudden for some reason the starter now won't turn over, with the ignition on all you hear is a soft "click". First thing that was replaced was the bulk head starter switch, same result, replaced the power cable to the starter motor, no change, sounds extreme but fitted a brand new starter motor, still no joy. I jumped the starter straight to the battery and the starter cranked perfectly, so starter motor and feed are Okay, I've checked the continuity of the cable solenoid switch and it's fine. So everything the starter side seems okay but as soon as I connect the two brown cables, one being the alternator and the other powering the rest of the electrical system I get nothing from the starter. There's obviously a short but I have no clue as to where, does anyone have any tips on fault finding to trace the short before I disconnect everything and start again, have to admit I'm suspecting the alternator but have no idea how to check that either. Can anyone offer any ideas please.
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Re: Annoying mystery electrical fault

Postby qwertyhenry » Thu Sep 07, 2017 9:02 am

try putting a jumper cable on the earth side of the battery and the other side onto the engine and try that just to see if a bad body earth
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Re: Annoying mystery electrical fault

Postby GraemeT » Thu Sep 07, 2017 9:48 am

Can you connect the two brown cables independently of each other if that's possible? Would maybe allow you to rule out one or the other of those circuits.

Alternatively - wire them in but unplug/unclip the wires from the back of your alternator - if it all works fine then that would ID the alternator as your suspect.
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Re: Annoying mystery electrical fault

Postby Custard » Wed Sep 13, 2017 8:08 pm

I would take the coil lead off if trying that, or the fan belt.

You should not run up an alternator without it being connected you can damage the regulator part of it.

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