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Shutting down alternator for wading


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I remember an article ages ago in one of the comics, possibly the LRO one where they waded wolfs windscreen-deep in the sea, that they shut down the alternator for wading.

Now, I'm guessing the ground the sense wire (warning light) to stop it from generating, and therefore nasty things are less likely to occur to the internals.

The question is - is it worth it, and am I right in the way to do it?

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I was gonna say similar.... Even then, water borne grit will still enter the device so when you spin it up again, not much changes....

If you want to stop charging, isolate the 12 volt feed wire that tickles the alternator into life... When you want to charge again, switch the feed back on again.

There is a risk however that one day you will forget to switch back on.. And of course it's just another set of wires to fail on you ....

Neil

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Firstly, whether it's charging or not, the carp still gets in there, and does the damage.

Secondly, the alternator is self-exciting, i.e. it uses some of the electricty it generates to charge the coil, I don't see how you can turn that off without some fiddling with the alternator to put a switch in somewhere between the regulator and the winding, and, with regard to my first point, what's the point?

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An alternator works ok in clean fresh water. If you really wanted to go wading in the sea then the salt water would certainly mess up the alternator.

The military will have a detailed process for this which will probably involve removing the alternator after wading in the sea and soaking it in a bucket of WD40 or similar.

With all that aluminium and steel I think the alternator would be the least of the problems after wading in the sea.

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I think the point is to avoid electrical damage - whatever happens it's getting dunked but most electronics are happy to be wet as long as they're not powered up when it happens. I guess that's why the MOD do it, just wondering if it was a worthwhile alternator-preservation technique or just an extra compliction - and I think I've got the answer, thanks folks! :D

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One of the main reasons for wanting to shut the alternator down is that there will be a return path between the +Ve output and ground. In fresh water, the resistance of the water is relatively high and so few detrimental effects occur. In salt water, the resistance is significantly lower. This has the effect that the water will start to electrolyse (split into oxygen & hydrogen), which are generally not good gases to have round the engine! The current flowing will also promote electrolytic corrosion on the alternator/ engine block.

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I turn my 2nd alternator on/off it is a 36v one and only runs the winch's, the idea was to save fuel and brush wear as it makes a difference when you drive 2000+ miles to events.

I have a 12v relay that is switched that cut's the power to regulator.

Peter

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One of the main reasons for wanting to shut the alternator down is that there will be a return path between the +Ve output and ground. In fresh water, the resistance of the water is relatively high and so few detrimental effects occur. In salt water, the resistance is significantly lower. This has the effect that the water will start to electrolyse (split into oxygen & hydrogen), which are generally not good gases to have round the engine! The current flowing will also promote electrolytic corrosion on the alternator/ engine block.

In salt water you will get chlorine liberated and sodium hydroxide produced which will soon eat the metal away! Don't forget that the alternator output terminal is still connected to the battery so as well as disabling the machine (by open circuiting a brush as JW said) you will need to isolate it from the battery.

Just disconnecting the battery without disabling the alternator will destroy the regulator.

If you don't want the electronics to get wet you could always remove the regulator and rectifier pack and put them in a water-tight box, but you will obviously need to extend the wires from the alternator.

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