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MG MG Y Type - Dynamo/regulator

The pain never stops. Brand new re-built engine and I now find the dynamo and regulator are not delivering the juice. Anybody know where to source at reasonable prices?

Thanks in advance
Murray
Murray

Murray,

Yes, go to the MG Show at Stoneleigh on February 24th and find Jim. He sells an excellent selection of overhauled dynamos, starters, wiper motors etc. If needed you should be able to find a voltage regulator as well. Take a note of the part number.
He is excellent value for money.

Ted
Ted Gardner

It may well be that either the dynamo is in need of an overhaul or the regulator needs adjustment as it is cutting out too soon. I would find a good Auto electrician who knows Regulators inside out as an incorrectly adjusted one is a huge fire risk and have him check it and the dynamo over.

Paul
Paul Barrow

Have you re-polarized the generator? If not, cross the field wire to ground for an instant.
Scott Barrow

Murray, I'm with Scott. When I got my car the generator didn't work too, but after cleaning the innards and repolarizing the ammeter jumped for joy with me.

If it isn't the polarizing I'm with Paul...
Willem van der Veer

Murry - You can test the dynamo on the car before proceeding further. Disconnect the wires from the dynamo and jumper the two terminals together. Connect an analog meter, set to read no more than 50 volts full scale, to the two jumpered terminals with the black meter lead to the two terminals and the red wire to earth (if the car is positive earth, otherwise, reverse the connections. Start the engine, but don't rev it up. Slowly increase the revs while watching the meter - you should see the meter reading climb as the revs increase. Don't allow the meter to go any higher that 20 - 25 volts as it will climb very rapidly beyond that point. If you can get 20 volts out of the dynamo with this test, it is good. It it will not go to 20 volts regardless of how high the engine is reved, the dynamo is in need of overhaul (don't let any shop tell you "it goes up to 15 volts so it is good" - that is not true. A good dynamo will continue to increase in voltage until it gets high enough to destroy itself if you dont limit it to the above voltage.

If the dynamo puts out the correct polarity voltage during this test, it doesn't need to be polarized. If the polarity is not correct, then you will need to be polarized. The easiest way to polarize it after doing the above test is to remove the jumper from the two terminals and attach a piece of wire long enough to reach th battery terminals, to the smaller of the two terminals on the dynamo. Quickly wipe the other end of the wire to the terminal of the battery that isn't connected to ground. You should see a small arc as you wipe the wire across the battery terminal, which indicates that you got current through the dynamo field windings and it is now polarized correctly.

If after doing the above, you still don't get any output from the dynamo/regulator, you will need to look to the regulator. For testing the regulator, contact Bob Jeffers at bobj50@comcast.net, he is the expert on regulators. Also, Bob makes a solid state regulator that he puts in the original case that you send him and calibrates the regulator to the generator used in your car. Cheers - Dave
David DuBois

To answer your origonal question Murray. I had to replace my regulator about 5 years ago and after checking round I went for a new one from Moss Bradford at £95. I also had the dynamo rewound for £125 by a local firm who reset the system for £57. No problems since and she copes with halogen headlights now.
Peter Vielvoye

This thread was discussed between 25/01/2008 and 28/01/2008

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