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MG TD TF 1500 - How to repolarize a generator?

Hello all,

I bought a new generator at an autojumble. There is a sticker on it, that it is positive earth.

My car is negative earth. How do I repolarize it?
It is still outside the car

Thanks in advance
Erik van Hardeveld

Connect a length of wire to the 'A' terminal of the Control Box (voltage regulator). Quickly swipe the opposite end of the wire two or three times across the 'F' terminal on the back of the generator. The 'F' terminal is the smaller of the two. There should be a small spark. Do NOT connect the wire to the generator or leave it in contact with the generator for more than a split second. Avoid touching the wire to anything else.
Steve Simmons

Hello Steve,
Thank you for your reaction.
Question: the generator is not in the car yet, so do I put it in the car first? Contact on or off?

Or can I repolarize it on the workbench?

Erik
Erik van Hardeveld

I would do it in the car.Then you know the polarity is correct.
Ray TF 2884
Ray Lee

You can do it on a bench but I agree, easier to wait until it's in the car.
Steve Simmons

OK guys, thanks.
Erik van Hardeveld

Changing polarity on my TF is a spring priority, but you make no mention of how the battery is connected when you do this procedure.

Before of after switching the battery?

Gord Clark
Rockburn, Qué.
Gord Clark

Hi Gordan. Thee are 3 devices in this network, a generator, a voltage regulator and a battery. Only one of them has an absolute polarity to start with, and that's the battery. Each battery terminal is solidly labelled, either positive or negative. You are going to connect the car's earth cable to one or the other. That is the one that determines the car's 'earth' polarity.

You will determine the car's operating polarity by 'polarizing' the car's generator. That's where the battery's other terminal comes into play. The smaller of the two terminals on the generator determines which polarity of voltage will be supplied by the generator. All you have to do is to do a quick swipe of a wire between the battery's non-earthed terminal and the small terminal of the generator. The generator frame needs to be connected to earth/ground while all of this is going on.

The third device, the voltage regulator, will learn about polarity when you connect it up. THAT's for an old-fashioned voltage regulator. MODERN one's tend to have solid state devices that are polarity sensitive. If you apply the wrong voltage you're apt to leave the smoke out.

Hope this helps, Gord. Bud
Bud Krueger

This thread was discussed between 25/01/2025 and 19/02/2025

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