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TR2/3/3A TR3 New Generator

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M

Mkutz

Jedi Hopeful
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Hi TR3 Folks -- I'm installing a new generator in my TR3 and recall I need to set the polarity. The car is positive ground. The procedure, from recollection, involves taking a car battery with a wire connected to the positive (?) side and holding it to a terminal on the generator for a few seconds. Which terminal is it, the one on the back or the one on the side? Any clarification is appreciated!
 
Art, thanks for the link. I printed off the info and added it to my favorited list. Thanks to Mkutz for asking the question!

Tinkerman
 
I read the article, and it states that the polarization should be performed whenever the battery is disconnected.

Now I routinely "disconnect" my battery with a cutoff switch when the car is going to be sitting for a while. But I have never had to re-polarize the generator after disconnecting. Is this correct?

Thanks, Tim
 
It really depends on how long the battery is disconnected. There is residual magnetism in the pole shoes of the generator, but if disassembled or if the generator sits a long time, this magnetism dissipates. That's when it becomes neccessary to re-polarize. It sets the proper north-south relationship on the pole shoes and re-magnetizes them. How long this period of time is I couldn't tell you. I've seen poles shoes lose their magnetism within days, but most of the time it seems to last many months and sometimes longer.

Those "one-wire" alternators that seem to be popular replacements rely on the residual magnetism in the rotor poles to get them initially charging. If they sit for a long period of time and lose that magnetism, they'll never get going unless they get "juiced" again.

Edit: One more thing, just as a point of interest. When the armature is left in proximity of the pole shoes, the magnetism retains for a much longer period of time. Once the armature is taken away, the magnetism seems to dissipate much faster. We've run into this problem at work with late permanent magnet type starters. If the housings with the magnets in them are stored too long without armatures in them, they will start to lose their magnetism. We process the stuff too quickly through our plant to worry about it, but once we bought a bunch of new permanent magnet field housings that turned out to be no good because they were improperly stored. We had to send them back to be re-magnetized. :wall:
 
martx-5 said:
I've seen poles shoes lose their magnetism within days, but most of the time it seems to last many months and sometimes longer.
Click to expand...
Any kind of impact, like dropping the generator on the ground, can accelerate the loss, too. But I've seen them hold enough to get started for many years when left mounted on the engine.

That's interesting about the 1-wire alternators. I always assumed they just bled a few milliamps from the battery all the time, to keep the rotor magnetised. Can't see why anyone wouldn't want a warning light anyway, so I've never worried about it much.
 
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