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Dead Short, I Don't Mean Height


Manta again
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Ok here we go again. My wife went out in the car this morning when she got back she left the lights on again (3rd time but who's counting) our neighbour tried jump starting the car, the car tried to start once and then there was silence.

Just tried fitting a new battery when the positive terminal was connected there was alot of sparks and the short wire that earths the alternator to the engine (1.8 ohc engine) started to melt the covering.

Do we reckon the alternator is now scrap? does the alternator from the CIH engine fit? Good supplier of replacement part can I use an astra part.

Help needed again. Thanks

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Is this stating the obvious?

always remove the cable clamp from the negative terminal first. It’s marked with a minus (-) sign; the positive terminal has a plus (+) sign. Reverse the procedure, positive first, negative second, when replacing the cables.

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Leaving the lights on can flatten a battery very quickly and while they will sometimes charge back up often they won't. If its been done a couple of times the battery could be so flat that jump leads from another car still won't put enough power to start the car as the flat battery is sucking the power in and not letting it get to the engine.

As for the sparking and assuming you are fitting the battery terminals correctly then it does sound like the alternator is goosed.

Some small sparks when connecting the battery happens if something is turned on (like the lights) the electricity is just so darn eager to make things work it jumps across the gap as soon as the terminal is close.

For a lot of sparks and a melting wire it sounds like the windings in the alternator have shorted to earth and you're basically connecting the battery terminals together.

I would check by removing the power wire from the rear of the alternator and if its insulation is good secure it out of the way and make sure it can't touch anything. Then connect the battery again and see if everything else works (including trying to start the car)

That should tell you if its just the alternator at fault or if there is something more going on like a wiring fault.

If its just the alternator swapping it out for a good one should see you back on the road. I have at least one spare 1.8 alternator her if you need it.

Might then be worth fitting a headlight warning buzzer to make sure the headlights aren't left on again ;)

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Is this stating the obvious?

always remove the cable clamp from the negative terminal first. It’s marked with a minus (-) sign; the positive terminal has a plus (+) sign. Reverse the procedure, positive first, negative second, when replacing the cables.

It's stating the irrelevant.

Electricity doesn't care.

However, hrdrogen does.

The reason you connect the -ve last and disconnect it first is because when your spanner is on the -ve terminal, assuming it is bare steel, although it is live there is no potential difference (measurable voltage difference if you have a good earth lead) between it and the body, so if you catch anything except the live terminal with your spanner it won't short or create sparks because the sparks could ignite the hydrogen a charging or discharging battery can release. You can imagine what would happen it a spanner on the +ve caught the -ve body work or engine while undoing. If not removed quickly the short could cause a battery to pop as a spanner can flow huge current.

With things like car alarms fitted, stereos with memory or even just doors open there can be a little spark when sliding the terminals off the posts as there will be some current draw. Huge current draw is obviously the sign of something strange if ignition is off.

No warranty of any kind implied or given.

Back to the original point I would leave the battery off the car, if it was mine, and put my multimeter between the +ve and -ve battery terminals checking for continuity test, remove the fuses and then disconnect stuff until I have stopped the drain to make sure the fault was gone before reconnecting. But it's not mine and this is no form of recommendation.

No warranty of any kind implied or given and no liability accepted.

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"It's stating the irrelevant"

If that is so why do battery manufacturers give this advice?

For the reaons I wrote in the previous post.

Regardles of which terminal you put on first if there are some electrical circuits still on then which ever terminal you put on last becomes effectively the switch and will spark if sufficient draw. The ability to spark through an air gap is the same regardless of which one you put on first or last.

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Ok car is now sorted :) don't ask me how but the new starter motor was goosed :o some how shorting out. Refitted an older one and she now works fine. Did a few other jobs on her in preparation for the MOT which should be this week, just have to fix a leak from the manifold to downpie gasket and fingers crossed we can get on with our lives again. Thanks to all for your input.

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