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Dashboard voltmeter variation


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This gets weirder. Changed the rectifier pack to the old one, same result.

Put the bulb between the metal case of the alternator and the battery live…….same result but much brighter lamp. Dismounted the alternator completely and put the bulb between the battery live and the rocker cover (earth?) same result, flashing bright bulb? What’s going on? Not sure why it’s flashing. Bulb between positive and negative battery gives full on bright light.

Anyway I guess it means I’ve got a very slight connection to earth in my alternator hence the dim light, is that a concern or should I strip it down again and check my connections?

I’m confused.

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That flashing then is obviously nothing to do with the alternator.  If the bulb flashes when connected battery-to-engine but doesn't when connected directly across the battery, it suggests there is something weird going on with the earthing of the engine. Perhaps it is earthing somehow via the indicator or hazard flasher ?  Try a good earth strap to the engine and check the battery earthing to the body.  

I don't think there is anything wrong with the alternator now.  

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Firstly Rob H I need to apologise if I’ve wasted your time following my attempts to test the alternator……..I’m an idiot. Still a bit confused but a confused idiot.

I had the battery isolated using the isolator connector at the battery. I tested the bulb between the positive and negative terminals of the battery, all good as I said. However, when I was “testing” the alternator, for some reason I had the bulb between the negative terminal of the battery and the alternator. (As I said I’m an idiot!)The weird flashing must have something to do with the isolator I guess.

I have now done the test correctly, between the positive and the alternator, bulb did not light so all good. I think I’ll wait until tomorrow now to connect the alternator electrically to the car and test it with the engine running. Goodness knows what else I might do today.

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No problem Rob -we all do things like that.  Glad you sorted it and good luck. 

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Today’s another day and I’m not an idiot (today anyway).
I stripped the alternator down again completely and reinstalled everything, including the bearings, because there were a few things I hadn’t been happy with.

 I used my new 40w soldering iron to attach the wires to the slip rings, which was much better than before.

Installed in the car, bulb test done correctly this time, all good! Connected the socket and turned on ignition, ignition light on. Started the engine, ignition light out and voltage on the dashboard meter went up to 13.5 or 14V, better than its ever been since I’ve had the car. I am so happy today.

Thanks again for all the help and for putting up with my stupidity yesterday ;-)

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